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WORKS OF 
I^OF. R. C. CARPENTER 



PX7BUBHKD BT 



JOHN WILEY & SONS, INC. 



Hcatlnc and Vcntllatliw ot BuUdInc*. 

Sixth Edition, Revised and Enlarged. 8vo. 
xiv+598 pages, 290 figures. Cloth $3*50 net. 



By PROFS. CARPENTER AND DIEDERICHS 

Experimental Engineering and Manual for Testing. 

For Engineers and for Students in Engineering 
Laboratories. Seventh Edition, Rewritten and 
Enlarged. 8vo, xix + 1131 pages, 636 figures. 
Cloth, $6.00 net. 



HEATING AND VENTILATING 

BUILDINGS 



A MANUAL FOR HEATING ENGINEERS AND 

ARCHITECTS 



BV 

ROLLA C. CARPENTER, M.S., C.E., M.M.E., LL.D. 

Pkofessor Experimental Engineering, Cornell University 

Past President American Society Heating and Ventilating Engineers; 
Member American Society Mechanical Engineers 



SIXTH EDITION, REVISED AND REWRITTEN 
TOTAL ISSUE, TWELVE THOUSAND 



» • . * • - 



NEW YORK 

JOHN WILEY & SONS, Inc. 
London: CHAPMAN & HALL, Limited 

191S 



Cop3iTii^ht. iJjs. i>o». 1909. 1915 
ROLLA C. CARPENTER 



THK SCIENTIFIC PRESS 

NOBCflT DRUMMOND AND COMPANY 

BROOKLYN. N. Y. 



-1- / J ^ 

19 15 



PREFACE TO SIXTH EDITION. 



The first edition of this work was published in 1895, since 
which time five complete editions have been printed and sold. 
The sixth edition has been very largely rewritten and con- 
siderable new matter added; the size of the book as compared 
with the first edition being increased by neariy one-half. Since 
the first edition, several new chapters have been added : relating 
to fans or blowers for moving air; to the general subject of 
mechanical systems of heating and ventilating; to school- 
house heating and ventilation; and to air conditioning. It 
is believed that the book in its present form describes the 
latest improvements in the art of heating and ventilating; 
it also gives directions for the construction and installation of 
all the various systems of heating and ventilating now in use. 

The writer is under obligation for assistance and material 
in preparing the sixth edition of this book to the various 
heating engineers who have taken active part in engineering 
societies and in the technical papers devoted to the subject 
of heating and ventilation, to various practicing engineers, 
and especially to C. K. Carpenter, M.E., of Harvard Uni- 
versity, L. A. Wilson, M.E., of Cornell University, and W. M. 
Sawdon, M.M.E., of Cornell University, who did the greater 
part of the labor of preparation of the new edition. 

The purpose of the book is clearly set forth in the following 
extract from the perface of the first edition: 

The art of heating and ventilating buildings is that branch 
of engineering which is devoted to a practical application of 
the general physical laws of heat, of pneimiatics, and of hydrau- 
lics to the construction of heating and ventilating apparatus. 
The object of the book is to present to the reader, in as con- 



lU 



40508 



iv PREFACE TO SIXTH EDITI05. 

cise a fann as possible^ a general idea of the princqdes which 
apply, and of the methods of constructKXi which are in use at 
the present time^ in various sj^tems of heating and ventilating. 
In preparing the book, the writer has endeavored to present, 
in as clear and concise a manner as possible, first, a state- 
ment of the general principles of pure science which apply, 
second, a discussion of data and results of important investi- 
gations for showing the application of rational principles to 
practical construction; third, the various practical methods 
employed in heating and ventilating buildings: fourth, the 
methods of designing various systems of heating and venti- 
lating; fifth, a collection of useful tables for practical appli- 
cation of the principles stated. 

The writer has endeavored to arrange the matter so that 
it can be understood by any person possessing a thorough and 
practical knowledge of English and Arithmetic. Algebraic 
demonstrations and formulae, when introduced, are usually 
printed in smaller t>'pe; and if a general conclusion is deduced 
by algebraic methods it is usually restated in the form of a 
rule of practice. 

It has been the desire of the writer to arrange the work 
in a scientific manner, and to give methods or rules of practice 
which are based, as far as possible, on a rational foundation. 
In the case of nearly ever>' system of heating this has been 
possible. It is believed in this respect that the book will be 
an improvement over anything }vhich has preceded it. 

The lxK>k generally presents such information as the writer 
has found in an extensive practice in the erection and operation 
of heating apparatus to be that which is required by contractors 
and by engineers in charge of the erection of plants. 

For the litcrar>' part of the work obligation is due to nearly 
every writer who has preceded him. In nearly ever>- case 
special credit has been given, but in the back part of the book 
will be found a complete list of authorities. The writer has 
had the cordial assistance of many noted heating engineers, 
many manufacturers of heating apparatus, and all the pub- 
lishers of current literature devoted to this subject. 



PREFACE TO SIXTH EDITION. v 

The principal portion of the practical part of the book 
is devoted to construction of gravity-heating systems, using 
steam and hot water; but systems of heating with hot air, 
with or without blower, with exhaust steam and with elec- 
tricity, are considered, and practical directions for construc- 
tion are given. The general character of the contents will 
be best seen by consulting the table which follows. 

Ithaca, N. Y., 

December 15, 19 14. 



TABLE OF CONTENTS. 



CHAPTER I. 

NATURE AND PROPERTIES OF HEAT. 
ARTICLE PAGB 

1. Demand for Artificial Heat i 

2. Magnitude of the Industry of Manufacturing and Installing Heating 

Apparatus i 

3. Nature of Heat 2 

4. Measure of Heat — Heat-unit 4 

5. Relation to Mechanical and to Electrical Units 4 

6. Temperature — Absolute Zero 5 

7. Thermometer Scales 7 

8. Special Forms of Thermometers .• 9 

9. Electric Resistance Thermometers and Pyrometers 11 

10. Maxima and Minima Thermometers 15 

1 1 . Use of Thermometers 15 

1 2. Specific Heat 16 

13. Latent Heat 17 

14. Radiation 18 

15. Reflection and Transmission of Radiant Heat 19 

16. Diffusion of Heat 20 

1 7. Conduction of Heat 20 

18. Convection, or Heating by Contact 22 

19. Systems of Wanning 23 

CHAPTER II. 

PRINCIPLES OF VENTILATION. 

20. Relation of Ventilation to Heating 24 

21. Composition and Pressure of the Atmosphere 24 

22. Diffusion of Gases 27 

23. Oxygen 28 

24. Carbonic Acid, or Carbon Dioxide, CO2, and Carbonic Oxide, CO 28 

25. Nitrogen — Argon 30 

26. Analysis of Air 31 

27. Approximate Methods of Finding Carbon Dioxide (CO2) ss 

28. Humidity of the Air 36 

29. Measurement of the Relative Air Supply 39 

30. Influence of the Size of the Room on Ventilation 43 

vn 



viii TABLE OF CONTENTS. 

ARTIOLB PAGE 

31. Force for Moving the Air *. . 45 

32. Measurements of the Velocity of Air 46 

33. Calibration of the Anemometer 50 

34. The Effect of Heat in Producing Motion of Air 53 

35. Distribution of Air 56 

36. The Outlet for Air 58 

37. Ventilation-flues 61 

38. Summary of Problems of Ventilation 62 

CHAPTER ni. 

AMOUNT OF HEAT REQUIRED FOR WARMING. 

3^. Loss of Heat from Buildings 64 

40. Loss of Heat from Windows 64 

41. Loss of Heat from Walls of Buildings 66 

42. Heat Required for Purposes of Ventilation 69 

43. Total Heat Required 70 

44. Peclet's Computation of Loss of Heat through Walls and Windows 73 

CHAPTER IV. 

HEAT GIVEN OFF FROM R.\DIAT1XG SIRFACES. 

45. The Heat Supplied by Radiating Surfaces 81 

46. Heat Emitted by Radiation S2 

47. Heat Removed by Convection (Indirect Heating) 84 

48. Total Heat Emitted 85 

49. Heat Transmission Varies with Circulation 8q 

50. Methods of Testing Radiators po 

51. Measurement of Radiating Surfaces 94 

$2. Effect of Painting Radiating Surfaces 05 

53. Results of Tests of Radiating Surface q/) 

54. Tests of Indirect Heating Surfaces 104 

5$. Conclusions from Radiator Tests 108 

Temperature Produced in a Room by a Given Amount of Surface when 

Outside Temperature is High 1 1 1 

Correcting for the Wind Velocity 113 

Protection of Main Pipe from Loss of Heat 113 

Pipe Coverings 117 

Tests of Pipe Coverings i iq 

Transmission of Steam Long Distances up 

CHAFFER V. 

FLOW OF WATER, STEAM AND AIR. 

Flow of Water and Steam. . . .... ... 1 24 

Gravity Hot Water \2$ 

Flow of Water through Pi|x'> 128 



TABLE OF CONTENTS. ix 

ARnCLB PAGE 

The Flow of Air and Gases 130 

Experiments on the Flow of Steam through Pipes 135 

Charts for Flow of Steam in Pipes 141 

Dimensions of Registers and Flues 142 

Dimensions of Registers 144 

Size of Ducts for Indirect Heating 144 

Roof Ventilators 147 

Power for Moving Air through Ventilating System 147 

CHAPTER VI. 

PIPE AND FITTINGS USED IN STEAM AND HOT-WATER HEATING. 

$6. General Remarks .' . 148 

57. Cast-iron Pipes and Fittings 148 

58. Wrought-iron and Steel Pipe 150 

59. Pipe Fittings 153 

60. Valves and Cocks 159 

61. Air valves 165 

62. Expansion-joints 169 

CHAPTER VII. 

RADIATORS AND HEATING SURFACES. 

[ 63. Qualities of an Efficient Steam Radiator 172 

64. Radiating Surface of Pipe 172 

65. Vertical-Pipe Steam-radiators 175 

66. Cast-iron Steam-radiators 176 

67. Hot-water Radiators 177 

68. Direct-indirect Radiators 182 

69. Indirect Heaters 182 

70. Proportions of Parts of Radiators 185 

CHAPTER VIII. 

STEAM-HEATING BOILRSS AND HOT-WATER HEATERS. 

1. General Properties of Steam — Explanation of Steam Tables 187 

2. General Requisites of Steam-boilers 188 

3. Boiler Horse-power 189 

4. Relative Proportions of Heating to Grate Surface 190 

5. Water Surface — Steam and Water Space 193 

6. Requisites of a Perfect Steam Boiler 194 

7. General Types of Boilers 195 

8. The Horizontal Tubular Boiler 197 

9. Locomotive and Marine Boilers 199 

80. Water-tube Boilers 200 

81. Hot-water Heaters 202 



X TABLE OF CONTENTS. 

AKTICLK PAGB 

82. Classes of Heating-boilers and Hot-water Heaters. 203 

83. Heating-boilers with Magazines 209 

84. Heating-boilers for Soft Coal 209 

85. Boilers in Batteries 210 

CHAPTER IX. 

SETTINGS AND AFPLLINCES — METHODS OF OPERATING BOILERS AND HEATERS. 

86. Brick Settings for Boilers 211 

87. Setting of Heating Boilers 215 

88. The Safety-valve 216 

89. Appliances for Showing Level of Water in Boiler 220 

90. Methods of Measuring Pressure 222 

91. The Bourdon Pressure Gauge 222 

92. Damper-regulators 224 

93. Blow-off Cocks and Valves 225 

94. Form of Chimneys 226 

95. Sizes of Chimneys 225 

96. Chimney-tops 228 

97. Grates 228 

98. Traps 230 

99. Return-traps 233 

100. General Directions for the Care of Steam-heating Boilers 236 

loi. Care of Hot-water Heaters 238 

102. Boiler Explosions 238 

103. Explosions of Hot-water Heaters 243 

104. Prevention of Boiler Explosions 244 

CHAPTER X. 

GRAVrrV STEAM-HEATING SYSTEMS. 

05. Systems Employed in Steam-heating 245 

06. Definitions of Terms Used 246 

07. S>'stems of Piping 248 

08. Pif)e Connections, Steam-heating Systems 251 

09. Piping for Indirect Heaters 254 

0. Vacuum Circulating Systems 255 

1. General Principles 257 

2. Amount of Heat and Radiating Surface Required for Warming 258 

3. Wolfe's Diagram 260 

4. The Amount of Surface Required for Indirect Heating 262 

5. Summary of Approximate Rules for Estimating Radiating Surface 266 

6. Computation of Steam Piping 268 

7. Rules for Steam Pipe Sizes 270 

8. Size of Return-pipes, Steam-heating 272 

9. Summary of Various Methods of Computing Quantities Required 
lor Hf ting 274 

<t Method of Computing Radiation 276 



TABLE OF CONTENTS. XI 

CHAPTER XI. 

PUMP RETURN STEAM-HEATING SYSTEMS. 
AKTICLB PAGE 

30. General Remarks 280 

31. Systems of Exhaust Heating 281 

32. Proportions of Radiating Surface and Main Pipes Required in Exhaust 
Heating 282 

33. District Heating 286 

34. Systems of Exhaust Heating with Less than Atmospheric Pressure 286 

35. The Webster System 289 

36. Diagrams with Cochrane Steam Stack Heaters 292 

37. The Paul System 294 

38. The Johnson System of Hermetic Heating 297 

39. Combined High- and Low-pressure Heating Systems 298 

40. Pump Governors 298 

41. The Steam Loop 300 

42. Reducing Valves 302 

43. Transmission of Steam Long Distances 303 

44. Pipe Sizes for Vacuum Steam Heating Systems 30$ 

CHAPTER XIL 

HOT-WATER HEATING SYSTEMS. 

14$: Gravity Circulating System 306 

146. Methods of Piping Used in Hot-water Heating 306 

147. Expansion-tank 309 

148. Closed Systems 310 

149. The Honeywell Pressure System 312 

150. Accelerated Hot-water Systems 313 

151. Hot-water Circulating Systems 313 

152. Pipe Connections, Hot-water Heating Systems 315 

153. Position of Valves in Pipes 318 

154. Sizes of Pipes for Hot-water Radiators 319 

155. Combination Systems of Heating 323 

CHAPTER XHL 

HEATING WITH HOT AIR. 

156. General Principles 327 

157. General Form of a Furnace 329 

158. Proportions Required for Furnace Heating 331 

159. Air-supply for the Furnace 335 

160. Pipes for Heated Air 336 

i6x. The Areas of Registers or Openings into Various Rooms 339 

162. Circulating Systems of Hot Air 341 

163. Heating with Stoves and Fireplaces 341 

164. General Directions for Operating Furnace 342 



xii TABLE OF CONTENTS, 

ARTICLE PAGE 

165. Practical Arrangement of Furnaces 343 

166. The Federal Furnace League 346 

167. Rules for Furnace Heating 350 

168. Abstract for Furnace Specifications 350 

CHAPTER XIV. 

MECHANICAL VENTILATORS. 

169. General Conditions 352 

170. Steel Plate Fans or Blowers 353 

171. The Guiba) Chimney 356 

172. Multivane Fans 357 

1 73. Propeller or Disk Fans 359 

1 74. Volume or Positive Blowers 361 

1 75. Theoretical Work of Moving Air 361 

176. Work of Moving Air through Pipes 365 

177. Dimensions of Pipe-lines for Air 366 

Formulas for Approximate Dimensions and Capacities of Fans 368 

178. Characteristic Curves of Multivane Fans 371 

179. Maximum Pressure Produced by Fan or Blower 373 

180. Velocity and Volume 377 

181. Work Required to Run a Fan 379 

182. Application of Theory 379 

183. Practical Rule for Capacity 380 

184. Practical Rule for Power 381 

185. Tests which Verify the Rules 381 

186. Relative Efficiency of Fans or Blowers and of Heated Flues 382 

187. Disk and Propeller Fans 387 

188. Measurement of Air Supplied to a Room 388 

189. Introduction of Air into Rooms 389 

CHAPTER XV. 

HOT BLAST HEATING. 

190. General Remarks 392 

191. Various Forms of Met'hanical Ventilating and Heating Systems 392 

192. Volume- or Regulating-dampers 396 

193. Form of Steam-heated Surface 397 

194. Ducts or Flues — Registers 398 

195. Blowers or Fans 403 

196. Heating Surface Required 404 

197. Size of Boiler Required 405 

198. Practical Construction of the Hot-blast System of Heating 406 

199. Description of Mechanical Ventilating Plant 408 

200. Tests of Blower Systems of Heating 4x5 

aoi. Charts for Vento Heaters 420 

103. Table for Wiought-iron Pipe Heaters 421 

CmbA^* Theaiy of Convectioo with Forced Ventilation 424 



TABLE OF CONTENTS. xiii 

CHAPTER XVI. 

HEATING WITH ELECTRICITY. 
ARTICUt PAGB 

204. Equivalents of Electrical and Heat Energy 427 

205. Expense of Heating by Electricity 427 

206. Formulae and General Considerations 430 

207. Construction of Electrical Heaters 434 

208. Connections for Electrical Heaters. - 43$ 

CH.\PTER XVn. 

TEMPERATURE REGULATORS. 

209. General Remarks 436 

210. Regulators Acting by Change of Pressure 43^7 

211. The Powers Regulator 438 

212. Regulators Operated by Direct Expansion 441 

213. Relative Rates of Expansion 442 

214. Regulators Operated with Motor — General Types 442 

215. Pneumatic Motor System 444 

216. Construction of Pneumatic Thermostat 446 

The Johnson Positive Thermostat 449 

Johnson Intermediate Thermostat 450 

217. Humidity Regulators 451 

218. Saving Due to Temperature Regulation 451 

CHAPTER XVni. 

SCHOOLHOUSES, SHOPS, AND GREENHOUSES. 

219. Schoolhouse Warming and Ventilating 453 

220. Complex Character of the Problem 453 

221. Relation of Pure Air to Vitality 454 

222. Limitations to the Supply of Pure Air 454 

223. Draughtiness in Large Halls 454 

224. Means for Reducing Draughtiness 455 

225. Little Draughtiness in Outflowing Currents 457 

226. Air-supply for Schoolroom 457 

227. Cost 458 

228. Methods of Saving Heat 458 

229. Successive Ventilation 458 

230. Supply of Air for Rooms not Frequently Occupied 459 

231. Course of Air Supply 460 

232. Quick Preparatory Warming 462 

233. Warming by Rotation 462 

234. Heat Conunonly Wasted 463 

235. Solar Heat 463 

236. Automatic Control of Temperature 464 

237. Double Glazing 464 



2 HEATING AND VENTILATING. 

can be readily bought on the market in ahnost every form, 
from that of the simplest to that of the most complicated 
design. 

The exact amount of capital invested in this industry could 
not be determined from the census of 1910, as only a part of 
this industry is separably reported. Under the heading of 
*' Stoves and Furnaces, including Gas and Oil Stoves," there 
are reported 576 establishments, with 42,921 persons engaged 
in the industry, and with a combined capital of $86,944,000, 
and a yearly output to the value of $78,853,000. The man- 
ufacture of steam fittings, etc., and the installation of the 
heating apparatus is not included in the above heading, which 
probably would give more than double the capital and yearly 
output, so that both the probable capital invested and the value 
of the yearly output will each be in the neighborhood of $2 
per inhabitant of the United States. 

3. Nature of Heat. — Before consideration of the methods 
of utilizing heat in warming buildings a short discussion of 
the nature and scientific properties of heat seems necessary. 

Heat is recognized by a bodily sensation, that of feeling, 
by means of which we are able to determine roughly by com- 
parison that one body is warmer or colder than another. From 
a scientific standpoint heat is a peculiar form of energ)', similar 
in many respects to electricity or light, and is capable, under 
favorable conditions, of being reduced into either of the above 
or into mechanical work. We shall have little to do with the 
theoretical discussion of its nature, but, as it is well to have a 
distinct understanding of its various forms and equivalents, 
we will consider briefly some of its important properties. 

Heat was at one time considered a material substance which 
might enter into or depart from a body by some kind of con- 
duction, and the terms which arc in use to-day were largely 
founded on that early idea of its material existence. The 
theor}' that heat is a form of energy and is capable of trans- 
formation into work or electricity is thoroughly established 
by fact and experiment. It probably produces a molecular 
motion among the particles of bodies into which it enters, the 



NATURE AND PROPERTIES OF HEAT. 3 

rate . of such motion being proportional to the intensity of the 
heat. 

Heat has two qualities which correspond in a general way 
to intensity on the one hand and quantity on the other. The 
intensity of heat is termed temperature — this can be measured 
by a thermometer; while the quantity of heat is termed the 
British thermal unit, called the Thermal unit or the B.T.U., 
and is i/i8oof the amount of heat required to raise one pound 
of water from the freezing to the boihng point. The following 
sketch shows in a graphical manner, the relation between the 
temperature of water, and of dry air, and the amount of heat 
that each contains measured above the freezing-point of water. 

It is a fact which will appear from later statements that the 




At Atmospheric Pressure — 



Steam -i 



Quantity of Hcat-B.T.U.pcr Lb. 



200 400 000 800 1000 1200 

Fig. I . — Heat and Temperature Relation. 



amount of heat contained in two bodies of different kinds, but 
of the same weight and temperature, may be essentially dif- 
ferent. A familiar analogy might perhaps be seen in the case 
of the dimensions and weight of bodies. The weight depends 
upon the dimensions and the density of the material, for example; 
a ball of wood and an iron ball of the same dimensions would 
have quite different weights. In a similar manner the amount 
of heat depends upon the temperature and also upon the weight 
of the body and that property of the material termed its specific 
heat. In addition, when a solid material is melted or a liquid 
is boiled, a considerable amount of heat is added in effecting 
the change of state of the material without raising its tem- 
perature. 

Note that heat is equivalent, not to mechanical force, 



4 HEATING AND VENTILATING. 

but to mechanical work. Work, defined sdentifically, is the 
application of force in overcoming some resistance; it is the 
result of a force acting through a certain distance, the distance 
moved through having as much effect on the result as the force 
acting. The work done is proportional to the product of the 
force exerted, multiplied by the space passed through. In 
English measures the imit of this product is a foot-pound . which 
signifies one pound raised to a height equal to one foot; it is 
itself a complex quantity resembling heat in this req)ect. Heat 
can be transformed into work. 

4. Measure of Heat — ^Heat-imit. — As explained heat can- 
not be measured by the thermometer; it can, however, be 
measured by the amoimt that some standard is raised in tem- 
perature. The standard adopted is water, and heat is imiver- 
sally measured by its f>ower to raise the temperature of a given 
weight of water. In English-speaking countries the mean 
heat-unit is 1/180 of the heat required to raise one p>oimd of 
water from the freezing to the boiling point, and this quantity 
is termed a British thermal unit; this will be referred to in this 
work by its initial letters B.T.U., or simply as a heat-unit. 
The amount of heat required to change the temperature of one 
pound of water one degree is not the same at all temperatures; 
the variation, however, is slight and for practical purposes can 
be entirely disregarded. The unit of heat used by the French 
and Germans, and for scientific purposes generally, is called 
the calorie; it is equal to one kilogram (2.205 pounds) of water 
raised one degree centigrade (1.8 degrees Fahrenheit) and is 
equal to 3.967 B.T.U. The calorie is referred to water at a 
temi)crature of 15-16° Centigrade (59-60.8 degrees Fahrenheit). 

5. Relation to Mechanical Work and to Electrical Units. — 
The relation of heat to mechanical work was accurately meas- 
ured by Joule in 1838 by noting the heating effects produced 
in revolving a paddle-wheel immersed in water. The wheel 
being revolved by a weight falling a given distance, the mechan- 
ical work was known; this compared with the rise in tem- 
perature of the water enabled him to determine that the value 
of one heat-unit estimated from 39° to 40° F. was equivalent 



NATURE AND PROPERTIES OF HEAT. 5 

to 772 foot-fwiinds. Later investigation has slightly increased 
this result, so that when reduced to a temperature of 62 degrees 
F., and for this latitude, it is 6 foot-pounds greater, so that at 
present the work equivalent of one heat-unit is generally regarded 
as 778 foot-pounds. This signifies that the work of raising 
I lb. 778 feet is equivalent to the energy required to change the 
temperature of i lb. of water from 62 to 63 degrees F. 

The equivalent value of heat and mechanical work is now 
thoroughly established, and imder favorable conditions the one 
can always be transformed into the other. As illustrations of 
the transformation of heat into work we have only to consider 
the numerous forms of steam-engines, gas-engines, and the 
like. A transformation from mechanical work into heat is 
shown in the rise of temperature accompanying friction in the 
use of machines of all classes. The heat produced in the per- 
formance of any mechanical work is exactly equivalent to the 
work accomplished, 778 foot-pounds of mechanical work being 
p)erformed in order to produce a heating effect equivalent to 
raising i lb. of water 1° F. 

The term horse-power has been used as the measure of the 
amoimt of work. It has been fixed as 33,000 foot-poimds per 
minute. This is equivalent to 42.42 B.T.U. per minute, or 
to 746 watts in electrical measures. For the work done in 
one second the above numbers should be divided by 60; for 
that done in one hour they should be multiplied by 60. In all 
English-speaking countries the capacity of engines and machin- 
ery in general is expressed in horse-power, so that it is necessary 
to become familiar with this term and its equivalents in heat 
and electrical units. 

6. Temperature — Absolute Zero. — One of the properties of 
heat is called temperature; this property can be measured 
by a thermometer and is proportional to the intensity of the 
heat. All our knowledge of heat as obtained by the sensation 
of feeling deals only with the temperature and the terms in 
common use by means of which bodies are compared and 
denominated hot, hotter, hottest, have reference not to the 
heat actually in the different bodies but to the temperature. 



* HEATT5G A^n> VE3rni-lTCTO, 

There a ^wa.-^-? st tendtncv ioz btsLt to dbv titroozfi inteF- 
vficuoj^ nmimma from st brjtter ti> a colder body anrf there 
U ar> tttKfcncj' for bcsu to Sow firom a cold to a hot body* 
althou^ the relath'e amotoiti ot beat m. the two bodies might 
be dxffftTWit from that indicated bv the thermometer. ThuSv 
a^ an fIIu3tra.tioti. a pound of water requires ab^at eight tfcnes 
a.% much beat to ntiie it one degree in temperature as a pound 
of iron, and hence when equal weights of both of these materials 
are at the same temperature the water contains eight times 
itA mrirJi heat as the iron, although in common parlance the two 
\xjfisfr^ would be equally hot. 

The tendency for the hotter body to cod off and gi^-e up 
(t^ h/:at if} surrounding objects is characteristic of all materials, 
and if no other heat were supplied all bodies would come sooner 
or Iat/;r U> one cr^mmon temperature- This temperature, when 
fin;illy reacherl by all bodies in the universe, will represent the 
ultimate: limit of all cooling and almost the entire absence of 
hiAt. It will be near abs^jlute zero for all thermometric scales. 
and no greater cold will be possible or even conceivable. The 
inUrr-pIanetarj- space is believed by many to be verj' nearly at 
thi.H limit, at the present time. Scientific men have made verj- 
careful determinations to ascertain what such a temperature 
mu.^t F>e, com[jarcd ^ith the ordinarj- thermometric scales. 

A i>erfcct gas which remains under constant pressure will 
contract in volume an amount directly proportional to the 
i hang«: of tcmfx-rature when reckoned from the point of great- 
e?it (oirl, which |K>int i.-^ known as the absolute zero. By experi- 
ment it i.-^ found that when air is at a temperature of ^2 degrees 
itn volume i,-^ rcrluccd one part in 492 whenever the temper- 
ature i.-* lowered one degree. From this fact it has been con- 
( luded that the absrjlute zero is 492 degrees on the Fahren- 
heit rtcale or 273 degrees on the centigrade scale, below the 
free/-ing-i)oint of water. Strictly speaking there is no perfect 
gas, yet the results obtained with dilTerent gases by different 
observers arc so nearly in accord that there is no question but 
that the results as given above are for all practical purposes 
correct. 



NATURE AND PROPERTIES OF HEAT. 7 

7. Tfaennometer Scales. — The thermometer is an instru- 
ment used to measure temperature. The effect of heat is to 
expand or to increase the volume of most bodies. For perfect 
gases the amount of this expansion is strictly proportional to 
the change of temperature; for liquids and solids the expansion, 
while not exactly proportional to the increase of temperature, 
is very nearly proportional to it, and these bodies can be used 
for an approximate and even a close measure of difference of 
temperature. In nearly all thermometers the temperature is 
measured by the expansion of some body, mercury, alcohol, 
or air being* conunonly used as the thermometric substance. 

The first thermometer was probably made by Galileo before 
1597. It consisted of a glass bulb containing air, terminated 
below in a long glass tube which dipped into a vessel contain- 
ing a colored fluid. The variations of volume of the enclosed 
air caused the fluid to rise or fall in the tube, the temperature 
being read by an arbitrary scale. Alcohol thermometers were 
in use as early as 1647, being made by connecting a spherical 
bulb with a long glass stem, on which graduations were made 
by beads of blue enamel placed in positions corresponding to 
one thousandths of the volume. 

Fahrenheit, a German merchant, in 1721 was the first to 
make a mercurial thermometer, and the instrument which 
he designed, with certain modifications, has been retained in 
use by the English-speaking people up to the present time. 
Fahrenheit took as fixed points the temperature of the human 
body, which he called 24 degrees, and a mixture of salt and 
sal-ammoniac, which he supposed the greatest cold possible, 
as zero. On this scale the freezing-point is 8 degrees. These 
degrees were afterwards divided into quarters, and later these 
subdivisions themselves, termed degrees. On this modified 
scale the freezing-point of water becomes 32 degrees, blood- 
heat 96* degrees, and the point of boiling water at atmospheric 
pressure 212 degrees. Unscientific as this thermometer is; 
it has been retained by two of the principal nations of the 

* As determined later, this should be 98°. 



8 



HEATING AND VENTILATING. 



world, the English and the American; it is awkward to use, 
it was borrowed from a foreign nation which had itself adopted 
a more scientific instrument, and except for the fact that it 
has been long in use it has not a single feature to recommend it. 

In 1724 Delisle introduced a scale in which the boiling- 
point of water was called zero and the temperature of a cellar 
in the Paris Observatory was called 100 degrees. This ther- 
mometer was used for many years in Russia, but is now obso- 
lete. In 1730 R6aumur made alcohol thermometers in which 
the boiling-f>oint of water was marked 80 degrees. This ther- 
mometer is still in use in Russia. 

Celsius adopted a centesimal scale in 1742 on which the 
boiling-p>oint was marked zero and the freezing-point of water 
100 degrees. This instrument is not now in use, although the 
centigrade scale is often called after Celsius. The. botanist 
Linnaeus introduced the centigrade thermometer, in which 
the freezing-point of water is marked zero and the boiling- 
point of water 100 degrees. This thermometer is now adopted 
for ordinary use by the nations of continental Europe and for 
scientific use by every nation in the world. 

The relative values of the degrees on the different ther- 
mometers used by various nations are given in the following 
table : 

TIIERMOMETRIC SCALES. 



Pahren- Centigrade, R^»- 
beit. mur. 



Degrees between freezing and boiling 

Temperature at freezing-point 

Temperature at boiling-point 

Comparative length of degree 

Comparative length of degree 

Countries where used 



iSo 

32 
212 

I 

I 

5/9 
England 

and 

America 



Celsius. 



100 


1 

80 




100 










100 


100 


. 80 







9/5 


■ 9/4 




9/S 


I 


: 5/4 




I 


France 


Russia 


Not 


in use 


and 








Germany 


1 







In all thermometric scales as given above, fixed points are 
determined by reference to the freezing and boiling points of 
water, with barometer at 29.92 inches, and most thermometers 



NATURE AND PROPERTIES OF HEAT. 9 

are constructed by marking these two points and then subdi- 
viding into the required number of degrees. The boiling- 
point of water changes with the atmospheric pressure and with 
the purity of the water, the greater the pressure the higher 
the boiling-temperature. A table on page 25 of this book 
shows the relation between the barometer pressure 
and the temperature of boiling water at atmospheric 
pressure. Mercury, alcohol, liquids and solids gen- 
erally do not expand uniformly for each degree of 
temperature, or, in other words, they are not per- 
fect thermometric substances. The error, however, is 
slight and is of more scientific than practical impor- 
tance. Any perfect gas, however, does expand uniformly 
and is a perfect thermometric substance, but gas 
varies in volume with slight change in barometric 
pressure, and, while of great value as material for a 
scientific thermometer, is too bulky and awkward for 
ordinary use. It is at the present time considered 
doubtful if there is any perfect gas in existence, or 
one which cannot be liquefied by intense cold and great 
pressure. Air, hydrogen, and nitrogen act like perfect 
gases at ordinary temperatures; the same is true in 
a slightly less degree of oxygen. Yet oxygen is a 
liquid whose boiling-point is 183 degrees centigrade 
(297 degrees] Fahrenheit) below zero. Nitrogen and 
air are liquids boiling at approximately 193 degrees 
centigrade (315 degrees Fahrenheit) below zero. Pictet 
and Cailletet have reduced the temperature to 200 p^^ ^ 
degrees C. below zero, finding air at that temperature 
to be a liquid as limpid as water and, like water, having a 
decided blue tint when seen by transmitted light. 

8. Special Forms of Thermometers. — The mercurial ther- 
mometers, as ordinarily constructed (Fig. 2), consist of a bulb 
of glass joined to a capillary glass tube filled so as to leave a 
vacuimi in the upper part of the glass stem, above the mer- 
cury; they cannot be used for any temperature higher than 
that of the boiling-point of mercury, which is about 675° F. 



10 



HEATING AND VENTILATING. 



-I B 



More recently these thermometers have been filled with nitro- 
gen or carbonic dioxide in the upper part of the glass stem, 
which by pressure prevents the mercury boiling. Thermom- 
eters constructed in this way can be used safely in temperatures 
as high as the melting-point of ordinary glass, say to 1000° F. 
Mercurial thermometers are made in various ways; the 
cheaper ones have graduations on an attached frame of wood 
or metal, but the more accurate and better grades have the 
graduations cut directly into the glass stem. Fig. 2. It has 
been found that the glass from which these thermometers are 
made changes volume slowly for many months after construc- 
tion, so that it is necessary to fill the thermometer with 
mercury a long time before graduation. In the better grade 

of thermometers the graduations are 
obtained by comparing point by 
point with an accurate standard; in 
the cheaper ones by simply subdivid- 
ing into equal parts between freezing 
and boiling points. At very low tem- 
peratures (—38° F.) mercury solidifies 
and its rate of expansion changes; 
alcohol or spirits of similar nature are 
not so affected, and hence are better 
suited for use in thermometers for 
measuring extremely low temperatures. 
Air thermometers, while difficult to 
use and of somewhat clumsy con- 
struction, are accurate through a wide range of temperature. 
These are made either by confining the air in a constant 
volume and measuring the increase in pressure (Fig. 3), or 
else by maintaining the pressure constant and noting the 
increase in volume. If the volume be maintained constant, 
the pressure will increase directly proportional to the increase 
in absolute temperature. In the air thermometer (Fig. 3) 
the volume is kept constant and the increase in pressure is 
measured by the rise of mercury- in the tube OC above the 
line AB, That is, in passing from the freezing to the boil- 




Fic. 3. — Air Thermometer. 



NATURE AND PROPERTIES OF HEAT. 11 

ing-point of water, the barometer being at 29.92, the pressure 
will increase 180/492, as expressed on the Fahr. scale, or 100/273 
on the Cen. scale 

The determination of temperature with the air thermometer, even if 
the instrument is calibrated to read in degrees, needs a correction for 
barometer-reading, since the height to which the mercury will rise in 
the tube wiU depend on the pressure of the air. The directions for using 
the instrument would be: ist. Find the constant of the instrument by 
putting the bulb in melting ice, and dividing the absolute temperature, 
492, by the siun of barometer-reading and reading of tube of the thermom- 
eter; 2d. To find any temperature, multiply the constant as found above 
by the sum of barometer-reading and reading of thermometer, and sub- 
tract from this product 460°. 

Note. — In using the instrument always keep the mercury at or near 
point i4, so as to keep volume of air constant. 

9. Electric Resistance Thermometers and Pjrrometers. — 

Instruments utilizing the change of electric resistance of metals 
with variations in temperature and the thermo-electric power of 
metals are used to indicate temperature. 

Electric Resistance Thermometer. — In this instrument use is 
made of the variations in the electric resistance of platinum wire 
with change of temperature. As electric resistances are measur- 
able with great accuracy, this method of estimating tempera- 
ture offers great sensibility. The resistance may be measured 
by balancing it against a known resistance by the use of a 
Wheatstone Bridge. This gives an instrument which is inde- 
j>endent of the accuracy of the galvanometer used to indicate 
a balance, but the apparatus must be adjusted by hand for each 
reading. 

The above principle is also applied in another form of instru- 
ment in which the resistance and therefore the temperature is 
indicated directly by the deflection of the pointer of an instru- 
ment similar to an ammeter. Fig. 4 shows a form of Electric 
Resistance Thermometer having an indicator of the Wheatstone 
Bridge type. This instrument is not in extensive commercial 
use. 

Thermo-electric Thermometer, — The electromotive force gen- 
jerated at the junction of two metals is a function of the temper- 



12 HEATING AND VENTILATING. 

ature, and as instruments are available for measuring dectro- 
motive forces with great accuracy, this principle is utilized to 
indicate temperature- 
There are a great many metals that could be used in con- 
structing the thermo-electric elements or thermo-couples, but 
platinuM and its alloys with iridium and rhoium have given the 




Fiu. 4. — Electric Resistaoce ThermometCT. 

best results and are generally used. In commercial instruments 
where extreme accuracy is not required, a high resistance milli- 
volt meter graduated to read the temperature in degrees directly 
is generally used as an indicator. This instrument is now in 
extensive commercial use. Fig. 5 shows one of these instruments 
arranged to indicate the temperature of a furnace. 

With either the resistance or the thermo-electric thermometer 
the " bulb " may be placed at any desired distance from the 



NATURE AND PROPERTIES OF HEAT. 



13 



indicator, and by providing suitable switches any number of 
bulbs may be used with one indicator. The resistance ther- 
mometer may be constructed to give the average temperature 
over a large area, while the thermo-couple gives the tempera- 
ture of a point. 

Metallic Pyrometers. — Most metals have rates of expansion 
which differ sensibly from each other, and this fact has been 
utilized in the construction of thermometers. 

Metallic thermometers are frequently used for high tem- 
peratures and have often been called pyrometers. If two bars 
of metal with unequal rates of expansion be fastened together 




Leads to Indicating Instrument 
Fig. 5. — ^Thermo-Electric Pyrometer. 



at one end and heated, the difference of extension of the two 
ends can be utilized in moving a hand over a dial graduated 
to show change of temperature (Fig. 6). The metal may also 
be bent into the form of a helix, in which case the heating will 
tend to change the curvature and thus move a hand which 
can be used to measure the temperature. 

A thermometer consisting of an iron bulb and a dial, very 
mucji like the metallic pyrometer in appearance, is made by 
filling the bulb with ether or hydrocarbon vapor, and con- 
structing it on the same principle as gauges used to register 
pressure on boilers. The vapor has a temperature correspond- 



14 



HEATING AND VENTILATING. 



ing to a given pressure, so that the dial can be calibrated to 
read in degrees of temperature instead of pounds of pressure. 

These instruments are extremely convem'ent and answer 
admirably for temperatures not exceeding looo® F. 

Calorimetric Pyrometers. — The principle of operation used in 
determining specific heat, Art. 1 2 , can, if the specific heat is known, 
be employed to ascertain the temperature of any hot body. 

Temperature by the Color of Incan- 
descetit Bodies atid by Melting-points. — 
Pouillet, as the result of a large num- 
• ber of experiments, concluded that all 
incandescent bodies have a definite and 
fixed color corresponding to each tem- 
perature. 

This color and temperature scale 
was given as follows: 




Fig. 6.— Metallic 
Pyrometer. 



Color. Temp. C. 

Faint red 525 

Dark red 700 

Faint cherry 800 

Cherry 900 

Brifiht cherry 1000 

Dark orange 1 100 

Bright orange 1 200 

White heat 1300 

Bright white 1400 

Dazzling white 1500 



1 
Temp. F. 


977 


1295 


1472 


1652 


1832 


2012 


2192 


2372 


2552 


2732 



This scale applies only to bodies 
that shine by incandescent light and 
not from actual combustion. A pyrom- 
eter making practical application of 
this scale has been invented by Noely 
and consists of a telescope with polarizing attachment and a 
scale so fixed as to read the angle through which a part of the 
instrument turns while a sudden transition of color takes place. 
Temperature by the Melting-points of Bodies.— The melting- 
points of bodies often provide an excellent means of deter- 



NATURE AND PROPERTIES OF HEAT. 15 

mining temperature. The temperature is obtained by using 
metallic alloys having known melting-points, it being higher 
than those which have melted, but lower than those which 
remain unmelted. A table of temperature of melting-points 
is given in the Appendix. In Germany a carefully prepared 
set of alloys cau be purchased for temperature determinations 
in this manner. 

ID. Maxima and Minima Thermometers. — The ordinary 
method of making a thermometer for recording the highest 
temperature is by introducing a small piece of steel wire about 
half an inch in length and finer than the bore of the thermom- 
eter into the tube above the mercury, in a merqiirial thermom- 
eter. The thermometer is placed with its stem, in a horizontal 
position, and the steel index is brought into contact with the 
extremity of the column of piercury. Now when the heat 
increases and the mercury expands the steel wire will be thrust 
forward; but when the temperature falls and the mercury 
contracts the index will be left behind, showing the maximum 
temperature. For showing minimum temperature a spirit 
thermometer prepared in a similar manner is used, as the spirits 
in contracting draw the index with the alcohol because of the 
capillary adhesion between the alcohol and the glass; but 
when the alcohol expands it passes by the index, without dis- 
placing it, so that its position shows the lowest temperature 
to which the instrument has been subjected. 

II. Use of Thermometers. — In the use of thermometers for 
determining the temperature of the air, they should be exposed 
to unobstructed circulation in a dry place and in the shade. 
Any drops of moisture on the bulb of the thermometer tend 
to evaporate and lower the temperature. For determining 
the temperature of steam or water under pressure thermometers 
are set into a brass frame so that they will screw directly into 
the liquid (Fig. 7) without permitting leakage. In other cases 
the thermometer can be inserted into a cup made as shown in 
Fig. 8. CyUnder-oil or mercury is put into the cup, and the 
reading of the thermometer will then indicate the temperature 
of the surrounding fluid. When the thermometer is inserted 



18 HEATING AND VENTILATING. 

into a cup some time will be required to obtiin the corre 
temperature. The temperature of steam-pipes or hot-waterl 
pipes camiot be obtained accurately by any system of applyiagl 
the thermometers externally to the pipes, and in case ther-i 
mometcrs are used they sliould be set deep into the current I 
of flowing steam or water, not placed in a pocket where airi 
can gather. 

12, Specific Heat.— The capacity which bodies have of J 
absorbing heat when changing temperature varies greatly;! 
for instance, the same amount of heat which would raise oncl 




Fic. ;.— Hoi Water Thcnnomctets. Straight and Angle Stems. 



pound of water one degree in temperature would raise about 
8 pounds of iron i degree in temperature or would raise i 
pound 8 degrees in temperature. The term used to express 
this property of bodies is specific heat, which is defined as 
follows: Specific heat is the quantity of heat required to raise 
the temperature of a body one degree, expressed in percent- 
age of that required to raise the same amount of water one 
degree, or in other words with water considered as one. Specific 
heat can always be found by heating the body to a given tem- 
perature. cooUng it in water, and noting the increase in tem- 



NATURE AND PROPERTIES OF HEAT. 



17 




Portable 
Sectional View. 



perature of the water. Thus if i pound of iron in cooling 8 

degrees heats one pound of water one degree, its specific heat 

is 1 = 0.125. A table of specific heats of the 

principal materials is given in the back of 

the book, from which it will be seen that 

the specific heat of water is greater than 

that of most other known substances. 

A knowledge of the specific heat of various 
materials is of considerable importance in 
the design of heating apparatus, since it 
indicates the capacity for heat for a given 
increase of temperature. The heat which 
is absorbed in raising the temperature of a Thi 
body is all given out when 
the body cools, so that although there is a 
difference in the amount absorbed, there is 
no difference in the final result due to heating 
and cooling. 

The total heat which a body contains is 
equivalent to the product obtained by multi- 
plying difference of temperature, specific heat 
and weight. The results will be expressed in 
heat-units or in capacity of heating one pound 
of water. 

The specific heat of bodies in general 
increases slightly with the temperature, the 
value in the table being the average from 
32° to 212°. 

13. Latent Heat.— WTien heat is applied 
to any liquid the temperature will rise until 
the boiling-point is reached, after which 
heat will be absorbed; but the temperature 
will not change until the entire process of 
evaporation is complete, or until the liquid is 
all converted into vapor. The heat absorbed during evap- 
oration has been termed latent, since it does not change 
the temperature and its effects cannot be measured by a 




18 



HEATING AND VENTILATING. 



thermometer. In the evaporation of water about five and 
one-half times as much heat is required to evaporate the 
water when at 212 degrees, into steam at the same temperature, 
as to heat the water from the freezing to the boiling point. Heat 
stored during evaporation is given out when the vapor con- 
denses, so that there is no loss or gain in the total operation 
of evaporating and condensing. A similar storage of heat 
takes place when bodies pass from the solid to the liquid state, 
but in a less degree. Although similar in some respects, latent 
heat differs in nature from specific heat. In both cases, heat 
not measured by the thermometer is stored; when the tempera- 
ture is lowered the stored heat is given up in both cases: in the 
first it represents a change in the physical condition, as from 
a solid to a liquid or a liquid to a gas; in the second the con- 
dition remains unchanged. 

14. Radiation. — Heat passes from a warmer body to a 
colder by three general methods, each of which is of consider- 
able importance in connection with the methods of heating. 
These methods are radiation, cofidtiction, and convection. The 
heat which leaves a body by radiation travels directly and in 
a straight h'ne until it is intercepted or absorbed by some other 
body. Radiant heat obeys the same laws as light, its amount 
varying inversely as the square of the distance, and with the 
sine of the angle of inclination. The amount of radiant heat 
which is emitted or which is absorbed depends largely, if not 
altogether, upon the character of the surface of the hot and 
cold body; it is found by experiment that the power of absorb- 
ing radiant heat is exactly the same as that of emitting it. 
The relative amount of heat emitted or absorbed by different 
surfaces is given in the following table. 

RELATIVE EMISSIVE POWERS AT THE BOILING TEMPERATURE 



Lamp-black 100 

White-lead '. . . ico 

Paper 98 

Glass 90 

India ink 85 

Shdlac 72 



Steel 17 

Platinum 17 

Polished brass 7 

Copper 7 

Polished gold 3 

Polished silver 3 



NATURE AND PROPERTIES OF HEAT. 19 

Radiant heat passes through gases without affecting their 
temperature or being absorbed to any appreciable extent. It 
is probably true that a very large body of air, especially air 
containing watery vapor, does absorb radiant heat, for it is 
known that the earth's atmosphere intercepts a sensible pro- 
portion of the heat radiated from the sun. 

15. Reflection and Transmission of Radiant Heat. — Radiant 
heat, like light, may be reflected and sent in various directions 
by materials of various kinds. Thus in Fig. 10, heat radiated 
from K is reflected to L, and vice versa. The following table 
shows the proportion of radiant heat which would be reflected 
by various substances: 

REI'I-ECTING POWER. 

Silver-plate 97 

Gdid 95 

Brass 93 

Speculum -metal 86 

Tin 85 

PoUshed platinum So 

Steel 8.) 

Zinc 81 

^™° " F'f- .-.— R-fl.--.r„n of Heat. 




Radiant heat also possesses the property of passing through 
certain substances in very much the same manner that light 
will pass through glass. This property is called diathermancy. 
The following table gives the diathermanous value of various 
substances, the heat being obtained from a lamp. The trans- 
mission power varies with the source of heat. 



crystjU-lized bodies mm mm. xincK. 

COLOKLESS. 



Rock-salt 9*'! 

Iceland sjiar. 1 3 

Rock-crTstal 57 

Brazilian tiqwu 54 

Carbonate of lead $2 

Borau of soda 38 

Sulphate <rf lime 10 

Citric acid.. 15 

Kodt-alum 13 



Smoky quariz (bniwn) 57% 

Aqua-marinn (liRht bluf) 19 

Yellow agate 29 

Green tourmaline 27 

Sulphate of copper (blue) □ 



20 HEATING AND VENTILATING. 

PER CENT OF HEAT TRANSMITTED THROUGH DIFFERENT 

SUBSTANCES. 

WHEN RECEI\'ED FROM AX ARGAND LAMP (DESCRY ID *S PHYSICS). 

SouDS. Liquids 9.21 mm. thick. 

Colorless Glass 1 1.88 mm. thick. Colorless Liquids. 

Flint-glass from 67 to 64% Distilled water 11% 

Plate-glass 62 to 59 Absolute alcohol 15 

Croi^-n-glass (French) 58 Sulphuric ether 21 

Crown-glass (EngUsh) 49 | Sulphide of carbon 63 

Window-glass 54 to 50 Spirits of turpentine 31 

Pure sulphuric acid 17 



Colored Class 1.85 mm. thick. 



Pure nitric acid 15 



Deep violet 53 Solution of sea-salt 12 

Pale violet 45 Solution of alum 12 

Very deep blue 19 " Solution of sugar 12 

Deep blue $^ Solution of potash 13 

Light blue 42 Solution of ammonia 15 

Mineral-green 23 



Apple-green 26 



Colored Liquids. 



Deep yellow 40 Nut-oil (yellow) 31 

Orange 44 Colza-oil (yellow) 30 

Yellowish red 53 . Olive-oil (greenish yellow) 30 

Crimson 51 Oil-camations (yellowish) 26 

J Chloride sulphur (reddish brown). 63 

! P\Toligneous acid (brown) 12 

] White of egg (slightly yellow) 11 

16. Diffusion of Heat. — Various materials possess the 
property of reflecting the radiant heat in such a manner as to 
diffuse it in all directions, instead of concentrating the heat in 
any one direction. If the heat were all returned, the tempera- 
ture of the body would not rise, but would remain constant. 
The diffusive power as determined by Laprovostaye and 
Desains was found to be as follows for the following substances, 
the heat received being 100: 

White-lead 82 

Powdered silver 76 

Chromate of lead 66 

17. Conduction of Heat. — WTien heat is applied to one 
end of a bar of metal it is propagated through the substance 
of the bar, produdng a rise of temperature which gradually 



NATURE AND PROPERTIES OF HEAT. 21 

travels to the remote portions. This transmission of heat is 
called conduction. It differs from radiation, first, in being 
gradual instead of instantaneous; second, in exhibiting no 
preference for travelling in straight lines, the propagation 
being as rapid through a crooked as a straight bar. In heating 
a body the heat is at first largely absorbed by the body with- 
out changing its temperature, then for a time it is applied in 
raising the temperature; the time required for this operation 
will depend upon its specific heat. After a certain time the 
temperature of the body will remain constant, the heat being 
removed as rapidly as it reaches a given position, and in this 
case we have an illustration of the transmission of heat by 
conduction. The amount of heat which passes is directly 
proportional to the area of cross-section, to the difference of 
temperature divided by the thickness, and to a coefficient 
which depends upon the character of the material. The coeffi- 
cient is the quantity of heat which flows, in unit time, through 
a cross-section of unit area, when the thickness of the plate is 
unity and the difference of temperature is one degree.* 

The conducting power of materials varies greatly. The 
metals are in general good conductors of heat, but differ greatly 
among themselves. The following table gives the relative 
values of the conducting powers for different metals: 

RELATIVE CONDUCTIXG POWERS. 



Silver loo 

Copper 65 lo 95 

Gold 53 

Brass '. 19 to 23 

Zinc 28 

Tin 14 



Steel 5 . 7 to 10. 2 

Iron 15 

Lead 7.6 

Platinum 8.2 

Palladium 6.3 

Bismuth i . 62 



Rocks and earthy materials have very much less power of 
conducting heat than the metals. Table XVII in Appendix 

* This can be expressed in a formula as follows: 

X 

in which 0=quantity of heat, i^ = coefficient, yl=area, «=thickness, /2— /i = dif- 
ference of temperature on the two sides of the plate. 



22 HEATING AND VENTILATING. 

of the fxx>k gives the value of the coeflSdent of various mate- 
rials in terms of the absolute amount of heat conveyed. The 
relative conductive powers of stone is about 4 per cent of that 
of iron and | of one per cent of that of copper. The conduct- 
ing power of woods does not differ greatly from that of water, 
and is alK->ut ij per cent of that of iron. The conducting 
pciwer of the air and gases is very small, and for practical pur- 
[x^ses may be considered as zero. As compared with iron the 
o^nducting power is about as i to 3500. A knowledge of the 
conduci;ive powers of bodies is of very great im|K)rtance in con- 
nection with the loss of heat in buildings of various dasses. 

The bodily sensation of heat or cold is affected to a great 
extent by the conducting power of the material with which the 
l>ody a>mc*s in contact. Thus if the hand were placed upon a 
metal plate at a temperature of 40 degrees, or plimged into 
mercury of the same temperature, a ver>' marked sensation of 
cold is experienced. This sensation is less intense with a plate 
of marl)le (if the same temperature, and still less with a piece 
of W(K)d. The reason is that the heat is more rapidly con- 
ducted away in the case of the metals, and this causes a more 
marked sensiilion of cold. 

Where heat is applied to one surface of a metallic body, it 
[>asses through the bcxly by conduction and is given off on the 
()[)[M)site side, usually to the air or to bodies in the surrounding 
r(K)ni, by radiation and convection. It will be found that the 
rate of conduction through the metallic body is many times 
greater than the rate of passage of the heat from the metallic 
substance. The knowledge of the conductive power is of little 
practiral imjM)rtancc, as regards heating surface, because of 
this fad, but it is of [^reat value in the selection of materials 
which will prevent the escape of heat from dwellings. This 
subject will be taken up in Chapter III, and applications given 
showing the loss of heat from different constructions of building. 

18. Convection or Heating by Contact. — When bodies are 
in motion there is more or less rubbing contact of their particles 
with each other and against stationary- objects. WTien the 
jmrticles rub against hot bodies they \\ill themselves become 



NATURE AND PROPERTIES OF HEAT. 23 

warm; it is only by such motion that liquids or gases can be 
heated any appreciable amount, The heating of the air of 
a room is practically all accomplished by currents, which brings 
the particles into contact with radiators, heated pipes, or even 
the walls of a room. If the air enters a room at a higher tem- 
perature, then by the reverse process the heat is given up to 
the colder objects, and the air is lowered in temperature. 
The heating of water in steam-boilers is largely due to a cir- 
culation which brings the particles of water in direct contact 
with highly heated surfaces, so that the heating in that case 
is accomplished largely by convection. 

19. Systems of Warming. — ^Any general consideration of 
a system of warming must include, first, the combustion of 
fuel which may take place in a fireplace, stove, steam or hot- 
water boiler; second, a system of transmission by means of 
which the heat shall be conveyed with as little loss as possible 
to the position where it can be utilized for heating; third, a 
system of diffusion of heat so that it shall be conveyed from 
any reservoir, radiator, etc., which is heated to objects, per- 
sons, or to the air of a room, in the most economical way 
possible. 

In case stoves are used the heat is directly applied by 
radiation and convection to heating the objects and air in the 
room in which the stove is placed. There is in this case no 
special system for the transmission of heat. In the case of hot- 
air heating, the air is drawn over a heated surface and then 
transmitted by pipes while at a high temperature to the rooms 
where heat is required. In the case of steam-heating, steam is 
formed in a boiler, transmitted through pipes to radiators 
which are placed either directly in the room or in passages 
leading to the rooms, and the condensed steam is returned 
either directly or by means of a pump to the boiler. In the 
case of hot-water heating the general system is much the same 
— water instead of steam circulates from the heater to the 
rooms where heat is required and back to the heater, the 
motive force which produces the circulation being the differ- 
ence in weight between the hot and cold water. 



CHAPTER n. 
PRINCIPLES OF VENTILATION. 

20. Relation of Ventilation to Heating. — Intimately con- 
nected with the subject of heating is the problem of main- 
taining air of a certain standard of purity in the various build- 
ings occupied. The introduction of pure air can only be done 
properly in connection with the system of heating, and any 
system of heating is incomplete and imperfect which does not 
provide a proper supply of air. 

The subject of ventilation often receives very little con- 
sideration in connection with the erection of apparatus for 
heating. 

21. Composition and Pressure of the Atmosphere. Atmos- 
pheric air is not a simple substance, but consists of a mechan- 
ical mixture of nitrogen and oxygen, together with more or less 
vapor of water', and almost always a little carbonic acid and 
a peculiarly active form of oxygen known as ozone. The 
nitrogen and oxygen are combined in the ratio of 79.1 to 20.9 
by volume, and these proportions are generally the same in 
all parts of the globe, and at all accessible elevations above 
the earth's surface. 

The amount of carbonic acid in the air varies in the open 
country from 4 to 6 parts in 10,000 by volume. The amount 
of moisture in the atmosphere sometimes forms 4 per cent of 
its entire weight, and sometimes is less than one-tenth of one 
per cent. 

The pressure of the atmosphere is measured by the height 
in inches at which it will maintain a column of mercury in an 
instrument called a barometer. The pressure of the atmosphere 
is less as the distance from the centre of the earth becomes 
greater. For that reason points of different elevation give 

24 



PRINCIPLES OF VENTILATION. 



25 



different average readings of the barometer. The normal 
reading of the barometer at sea level, which corresponds to a 
boiling-point for pure water of 212° F., is 29.905 inches. 

The pressure of the atmosphere, even at the same place, is 
constantly fluctuating with various conditions of the weather. 
The variation in barometer-reading from the mean may be 
1.5 inches in either direction. 

The fall of the barometer due to different elevations from 
the sea level would be approximately as follows: 



At 970 . 


Feet the barometer sinks 


I inch. 


*' 1970 


I < 


i ( 


2 inches 


'' 3000 


i » 


( ( 


3 " 


'' 4080 


( ( 


( ( 


4 " 


'' S190 


( k 


( ( 


5 " 



The atmospheric pressure has great effect upon the boiling- 
temperature of water; thus pure water will boil at the tem- 
peratures corresponding to the various barometric pressures^ 
as shown in the following table: * 



Boiling-temperature F. 


Barometer, 
Inches. 


Boiling-temperature F. 


Barometer, 
Inches. 


212 


29.905 


205 


25.990 


211 


29 331 


204 


25*465 


210 


28.751 


203 


24.949 


209 


28.180 


202 


24.442 


208 


27.618 


201 


23 943 


207 


27.066 


200 


23.453 


206 


26.523 







The weight of a cubic foot of air is inversely proportional 
to the absolute temperature; if freed from aqueous vapor and 
under a pressure of 30 inches of mercury, it weighs, according 
to Regnault, at o degrees F., 0.0866 pound. The rate of expan- 
sion in volimie or decrease in density is -— for each degree 



461 



Fahrenheit above zero. 



* Smithsonian Physical Tables, 1903. 



26 HEATING AND \TENTILATING. 

Table X in the Appendix gives the weights of air for different 
temperatures. For the temperature of 60® and 30" barometer, 
water is 814 times as heavy as air. Various other imits are 
sometimes used to measure the head or pressure, and for con- 
venience of reference these equivalents can be arranged as 
follows, standard pressure at sea level being 29.92 inches. 

30 inches of mercur>' = 14.73 lbs. pressure per sq. inch. 

=408 in. water = 33.92 ft. water. 

= 27750 ft. air at 60° Fahr. 
I inch water =0.577 oz. 

The atmosphere contains more or less impurities, in the form 
of dust, bacteria, and various gases. In places where the 
ventilation is poor, the air may contain carbon monoxide (CO), 
ammoniacal compounds, sulphureted hydrogen, and sulphuric 
and sulphurous and nitric and nitrous acids. It also contains 
some ozone, which is a peculiarly active form of oxj'gen, and is 
believed by many to have an important influence in the pres- 
ervation of the purity of the atmosphere. Authorities, how- 
ever, differ verj- ^-idely as to its distribution and action. A 
new constituent called argon has been discovered, which forms 
about I per cent of the atmosphere and being extremely inert 
k generally classed with the nitrogen in the air. 

Air contains more or less solid matter in the form of minute 
particles of dust. The dust particles are thought to bear an 
important part in the propagation and distribution of the bac- 
teria of various diseases, and also in the production of storms. 

Air contains microbe organisms, or bacteria, in greater or 
less numbers. The number of bacteria may be determined by 
slowly passing * a given volume of the air through a glass tube 
coated inside with beef jelly; the germs are deposited on the 
nutrient jelly, and each becomes in a few days the centre of a 
ver>' visible colony. In outside air the number of microbe 
organisms varies greatly, being often less than one per litre 
(61 cubic inches); in well-ventilated rooms they vary from 

* Enc>'c. Britannica, article " Ventilation." 



PRINCIPLES OF VENTILATION. 27 

I to 20, while in close schoolrooms as many as 600 per litre have 
been found. Camelley, Haldane, and Anderson found in their 
researches in mechanically ventilated schoolrooms an average 
number of 17 microbe organisms per litre. The results of 
stopping the mechanical ventilation was to increase the car- 
bonic acid without changing the number of microbe organisms. 

22. Diffusion of Gases. — Gases which have no chemical 
action on each other will, regardless of weights or densities, 
mingle with each other so as to form a perfectly uniform mix- 
ture. This peculiar property is called diffusion^ and is of great 
importance in connection with ventilation, since it indicates 
the impossibility of separating gases of different densities. 

Liquids of different densities do not make uniform mixtures, 
unless they have a special affinity for each other; the heavier 
invariably settles to the bottom. 

Perfect diffusion is a process which requires some time, so 
that the composition of samples from the same room may in 
some instances be sensibly different. The time required for 
the diffusion of gases is inversely proportional to the density, 
and directly proportional to the square root of the absolute 
temperature. Diffusion is a molecular action, and can be 
calculated from the kinetic theory of gases. One computation 
of this character indicates that the time required for the equal 
diffusion of carbonic acid throughout the atmosphere was 
2,220,000 years. 

Dr. Angus Smith found the following percentages of oxygen 
present in the air, in, samples collected in various places, which 
serve to show the variation which may exist under different 
conditions: * 



Seashore of Scotland, on the Atlantic 20 . gg% 

Top of Scottish hills 20.98 

Sitting-room, feeling close, but not excessively so 20.89 

Backs of houses and closets 20. 70 

Under shafts in metal mines 20. 424 

When candles go out 18 . 50 

When difficult to remain in air many minutes 1 7 . 20 



* Ency. Brit. 



28 HEATING AND VENTILATING. 

The variation in amount of carbonic acid is equally great, 
the quantity being as follows: 

London parks 0.0301% In workshops 0.3% 

On the Thames 0.0343 In theatres 0.32 

London streets 0.0380 Cornwall mines 2.5 

Manchester fogs 0.0679 

23. Oxygen. — Oxygen is one of the most important elements 
of the atmosphere, so far as both heating and ventilation are 
concerned. It is the active element in the chemical process 
of combustion, and also of a somewhat similar physiolo'gical 
process which takes place in the respiration of human beings. 
It exists in a free state mixed with about four parts of nitrogen 
in the air, and is essential not only for the support of any com- 
bustion, but for the support of life. It is not to be considered 
as haWng any properties as a food, but is rather the necessary 
element which makes it possible to assimilate and utilize the 
food. Taken into the lungs it acts upon the excess of carbon 
of the blood, and possibly also upon other ingredients, forming 
chemical compounds which are thrown off in the act of respira- 
tion. The chemical action of oxygen 'with the other elements 
can generally be considered as a sanitarj- one. In many respects 
the process of respiration resembles that of combustion; for 
in both cases oxygen is derived from the air, carbon or other 
impurities are oxidized, and the products of this oxidation are 
rejected. In both cases heat is given off as the result of this 
process. Its weight is sixteen times that of hydrogen. It is 
sometimes found in a peculiarly active form called ozone. 

24. Carbonic Acid or Carbon Dioxide, CO2, and Carbonic 
Oxide, CO. — The first is a product resulting from the perfect 
combustion of carbon; it is always found in small quantities, 
3 to 5 parts in 10,000 in the atmosphere of the country. 

This gas, although ver>' heavy as compared with that of 
pure air (44 times that of hydrogen), will, if sufficient time be 
given, mLx uniformly with the air. It is not a poisonous gas, 
although in an atmosphere containing large quantities of car- 
bonic dioxide a person might die from suffocation or for want 
of oxygen. 



PRINCIPLES OF VENTILATION. 



29 



While carbonic dioxide is not of itself injurious, yet as it 
is a product of combustion and respiration, and is usually 
accompanied with other injurious products, and for the lack 
of a better standard, it is regarded as an index of the quality 
of the air, and the amount of it present in the air is taken ais 
the standard by which we can judge of the ventilation.* In 
such a case pure air, containing 4 parts of carbon dioxide in 
10,000 would be the standard for comparison. Authorities 
differ as to the greatest amoxmt of carbon dioxide which might 
be permitted. It is quite certain that any unpleasant sensa- 
tion is not experienced imtil the amount is increased to 10 or 
12 parts in 10,000; yet authorities are generally agreed that 
the maximum amoxmt should not exceed 10 parts in 10,000 
at least for sleeping-rooms. The standard of good ventilation 
usually adopted at present would permit about 8 parts in 10,000 
in the air. There has been a tendency to make the standard 
of ventilation higher, thus requiring the introduction of greater 
quantities of air. 

The importance of the carbon dioxide test of air is too 
easily over-estimated. The CO2 percentage is used only as a 
measxirement of the vitiation of the air by respiration and com- 
bustion. Where CO2 is produced in such a manner that the 
oxygen in the air is not depleted or where the air is contamina- 
ted otherwise than by the presence of people, animals, or an 
open flame, the use of the CO2 test may give misleading results. 



♦ J. S. Billings, in his work on Ventilation and Heating, cites an experiment 
by Carnelley and Mackie, showing that the ordinary theory of increase of organic 
matter with increase of carbon dioxide is a reasonable one. The results of the 
experiment were as follows: 



Proportion of 

Organic Matter. 

Oxygen required to 

Oxidize 1,000,000 

Volumes. 



j Average 
Carbonic Acid 
in 10.000 
. Volumes 
' of Air. 



Number of 
Trials. 




30 HEATING AND VENTILATING. 

When air has a bad or a close odor it is generally objectionable^ 
even if it has a very low CO2 content. 

Carbonic acid is continually increased by the processes of 
combustion and respiration, yet for the past thirty years the 
amount in the air has not sensibly changed. 

Plant-growth and vegetable life assimilate carbonic acid 
and give off oxygen.* There exists in the air about 28 tons of 
carbonic acid to each acre of groxmd, yet an acre of beech- 
forest annually absorbs about one ton, according to Chevandier; 
and no doubt the total vegetation growing is sufficient to absorb 
the excess due to combustion and respiration, so that the total 
does not experience much change. 

Carbonic Oxide, CO. — This compound is not found in the 
air except under unusual circumstances. It is distinctly a 
poison, and has a characteristic reaction on the blood. Hem- 
pel, t the German chemist, experimented on its poisonous 
effects with a mouse. No symptoms of poisoning were detected 
until there were 6 parts CO in 10,000 of air, in which case after 
3. hours' time respiration was difficult; in another case the mouse 
could scarcely breathe in 47 minutes. With 12 parts in 10,000 
the mouse showed symptoms of poisoning in 7 minutes; with 
29 parts in 10,000 the mouse died in convulsions in about two 
minutes. 

25. Nitrogen— Argon. — The principal bulk of the earth's 
atmosphere is nitrogen, which is almost uniformly diffused with 
oxygen. This element is practically inert in all the processes 
of combustion or respiration. It is not affected in composi- 
tion either by passing through a furnace during combustion 
or in passing through the lungs in process of respiration. Its 
action is to render the oxygen less active, and to absorb some 
part of the heat produced by the process of oxidation. It is 
an element very difficult to measure directly, as it can be made 
to enter into combination with only a few other elements, and 
then under peculiarly favorable circumstances. 



* " How Crops Feed," by Johnson, page 47. 
t Hempei's Gas Analysis. Macmilian & Co. 



PRINCIPLES OF VENTILATION. 31 

A very small amoxint of ammonia, which is a compound of 
nitrogen and hydrogen, is found in the atmosphere. 

Water Vapor, — The atmosphere always contains more or less 
water vapor or moisture. The greatest amount of vapor that 
may exist in the air depends upon the temperature and varies 
from 0.00007 lb. per cu. ft. at 0° to 0.00282 lb. per cu. ft. at 
100° F. Besides controlling the rain fall the degree of satura- 
tion of the air with moisture influences health and to a large 
extent our bodily sensations of warm and cool air, by varying 
the rate of evaporation from the lungs and skin. 

26. Analysis of Air. — The accurate analysis of air requires 
the determination of aqueous vapor, carbon dioxide, carbon 
monoxide, oxygen and ozone, but for sanitary purposes the 
determination of carbon dioxide and water is the most fre- 
quently called for.* The nitrogen of the atmosphere cannot be 
determined by any known method of analysis; it is obtained by 
deducting the sum of all the other elements from the total. 
The approximate determination of the oxygen is done very 
readily by drawing a certain volume of the air into a measuring- 
vessel and then passing it over a mixture of pyrogallic acid 
and caustic potash or solid phosphorus; the oxygen is absorbed, 
reducing the volume of gas in amount proportional to the 
quantity of oxygen. This process is, however, not of extreme 
accuracy, and for minute quantities very much more complicated 
methods must be resorted to. In getting a sample of air to 
be analyzed, care should be taken that no air exhaled by the 
operator enters the sample. 

Method of Finding Carbon Dioxide (CO2). — The amount 
of this material present in the atmosphere is so small that the 
most delicate methods are required in order to measure it. 
The writer gives first an approved method which can be rapidly 
applied, and which is accurate to one part in ten thousand. 
This system of finding CO2 was devised by Otto Pettersson and 
A. Palmqvist, two European chemists. The instrument used 

*For a complete discussion of these various methods the reader is referred 
to " Gas Analysis ** by Professor L. M. Dennis, and published by The 
Macmilian Co. 



HEATING ASD VESTILATING. 



for this detenninatioQ is shown in Fig. 1 1 , and can be had from 
any dealer in physical apparatus. It consists of a measuring- 
vessel, A, connected with a U-shaped burette, B, from which 
commimication can be made by a small stop-cock, b; a manom- 
eter, fg, containing a graduated scale nearly horizontal; and 
two stop-cocks, / and g, by means of which communication 
can be made with the air. One side of this manometer, /, is 
in communication with the closed compensating vessel C; the 
other side can be put in com- 
munication with the measuring- 
vessel A . The burette B contains 
a saturated solution of caustic 
potash (KOH). The flask £ con- 
tains mercur}-, and by raising it, 
when the stop-cock c is open, the 
mercury- will rise in the flask A, 
and the air will be driven out. 
If the flask E be lowered the 
mercury- will flow from the meas- 
uring-tube, and the amount of 
air entering A can be measured 
by the graduations. When the 
measuring-tube A is full of air, 
the stop-cocks c. b. /, and g being 
open, the position of the drop of 
liquid in the horizontal tube of 
the manometer is accurately read. 
The stop-cocks c, a, J, and g are 
then closed, that at b opened, 
and the vessel E raised, drinng 
the air out of the measuring-tube .-! into the absorption 
burette B. This operation of raising and lowering the flask 
E is repeated several times; it is then lowered, and the 
air is drawn over into the measuring burette; the cock a is 
then opened and the vessel E manipulated until the reading 
of the manometer on the horizontal scale agrees with that in 
the beginning of the test. The reading of the graduated tube 




'in. 1 1. —Portable Form as 
Modified by Dr. Rogers. 



PRINCIPLES OF VENTILATION. 33 

A gives directly the amount of CO2. A slow motion screw 
is provided for accurately adjusting the mercury level. The 
caustic potash should on no account be allowed to get beyond 
its own stop-cock. The effect of changes of the barometer 
and of the air temperature and of the jacket water are eliminated 
by this apparatus, as the changes of volume are measured against 
an equal volume of untreated air confined in the compensating 
flask C. The determinations are made with air of ordinary 
hiunidity, and there is a very slight correction due to this fact, 
which is not likely to equal, in any case, one part of CO2 in one 
million parts of air. 

The methods of determining accurately the amount of car- 
bon dioxide in the air are in general based upon one of the 
three following principles: i, the measurement of the volume 
of carbon dioxide by methods similar to that already described 
and which, with proper precautions, is probably the most satis- 
factory of any device; 2, the determination of the amoxmt of 
carbon dioxide by the increase in weight of a substance, such as 
caustic potash, which is capable of absorbing it, and through 
which the air is passed. This is open to the practical difficulties 
of weighing very small quantities and of keeping the air per- 
fectly dry; 3, the transformation of the carbon dioxide in the 
air into a chemical compound by use of an absorbing chemical, 
as, for instance, caustic baryta, which is subsequently analyzed 
and the amoimt of the gas thus ascertained. This process 
was employed by de Saussure and Pettenkofer and requires 
extreme care and great skill in laboratory experiments. 

27. Approximate Methods of Finding Carbon Dioxide (CO2). 
— In addition to the accurate methods there are a number of 
approximate methods which may be used with satisfaction for 
the purpose of ascertaining the relative quality of the air as to 
whether good or bad, but which give no accurate indication of 
the percentage of carbon dioxide present. Some of the more 
important of these methods are described below. 

The carbocidometer of Professor Wolpert is highly recom- 
mended by Professor J. H. Kinealy. It consists of a glass 
cylinder about one inch in diameter and seven inches long, 



34 HEATING AND VENTILATING. 

closed at one end and provided with a rubber piston. The 
cylinder is graduated in cubic centimeters (c.c.) from the bottom 
upward to 50. The piston-rod is hollow and arranged to be 
closed by a rubber cap. A solution made by adding to one 
litre of water one-twentieth of a gram of sodic carbonate and to 
this .075 gram of phenolphthalein is reconunended. This 
solution is of a pink color so long as alkaline, but is made lighter 
in color by the addition of carbon dioxide, and it becomes 
colorless when made neutral. To use the Wolpert air-tester, 
press the piston down several times so as to drive the contents 
of the cylinder out through the hollow piston-rod, then add 
2 c.c. of the solution, then push the piston to the position show- 
ing 20 c.c. in the cylinder, and after stopping the piston-rod 
hole thoroughly shake the instnunent so that the solution will 
absorb the CO2. If the air in the cylinder is still pinkish, draw 
out the piston and add more air, then close the admission open- 
ing and shake as before. Continue this operation until the 
mixture in the cylinder is colorless. Tr\' this operation first 
in the outside air, then in the room where contents are to be 
tested. As an example, if the piston stands after this operation 
at 46 after using the outside air and at ^2 after using that in 
the room, deduct 2, since there is taken up by the solution 
2 c.c, leaving 44 and 30 as a remainder. We understand from 
this that the amount of CO2 in 44 c.c. of outside air would 
combine with the same amount of chemical as with 30 c.c. of 
the air from the room. Hence the amount of CO2 present 
in the room is to that in the air as 44 is to 30; that is, the air 
in the room would contain 1.46 as much CO2 as the air outside. 
If the air outside contain 4 parts in 10,000, that in the room 
would contain 5.84 parts in 10,000. Great care is needed to 
prevent the sodic carbonate from decomposing by exposure to 
the atmosphere. This apparatus can be purchased from dealers 
and importers in philosophical apparatus. 

Carbonic dioxide has the property of forming a precipitate 
in lime-water, thus rendering it turbid. Several methods of 
ascertaining the amount of COj in the air have been based on 
this property, all of which, however, arc extremely inaccurate. 



PRINCIPLES OF VENTILATION. 36 

The Smith method requires the use of six well-stoppered bottles 
holding respectively loo, 200, 250, 300, 350, and 450 c.c, a 
glass tube or pipette graduated to contain exactly 15 c.c. to 
a given mark, and a bottle of perfectly clear and transparent 
lime-water. The bottles are to be made perfectly clean and 
dry, then hlled with the air to be examined, then add to each 
of the bottles in succession, conmiencing with the smallest, 
15 c.c. of lime-water, shake thoroughly, and if txirbidity appears 
we have the following results: 

Contents of Bottle, c.c. Parts of CO2 in 10,000. 

ICO 16 

200 12 

250 10 

300 8 

350 7 

450 6 or less. 

The degree of turbidity can be determined by looking through 
the bottle at an ink-mark on a bit of white paper. 

There is another instrmnent of the same class as the Wolpert 
air-tester, in which is used, however, a test-tube holding 3 c.c. 
of lime-water with a white bottom on which is a black figure. 
Air is blown through by means of a rubber bulb containing 
28 c.c. which is fastened to a glass tube. The number of times 
which the bulb has to be filled and emptied in order to render 
the lime-water turbid determines the amount of CO2. If the 
bulb is discharged 40 times to produce opacity, we have 10 
parts in 10,000; if 50 times, we have 4 parts in 10,000, etc. 

The Lunge-Zeckendorf method is recommended by Billings 
as the most accurate of the ready methods of determining the 
amount of CO2 present in air, especially when it is in excess 
of 10 parts in 10,000. The analysis is made by the use of a 
solution consisting of desiccated sodium carbonate, 5.3 grams, 
dissolved in 1000 c.c. of distilled water which has been recently 
boiled and quickly cooled and to which one gram of phenol- 
phthalein is added. The apparatus consists of a bottle with 



36 HEATING AND VENTILATING. 

cubic contents of 125 cc, which is provided with a coA con- 
taining two glass tubes, one of which terminates near the top 
of the bottle, the other at the bottom. The short tube opens 
into the air, the other connects with a rubber tube leading to 
a bulb of 70 ex. capacity. The bulb is arranged to draw in 
air at one end and discharge through the rubber tube into a 
long glass tube leading to the bottom of the bottle. 

Wlien the analysis is to be made 4 cc. of the solution are 
added to 100 cc. of freshly boiled and cooled distilled water, 
and of this 10 cc are used for each determination by pouring 
in the bottle. The air is replaced by the air to be analyzed; 
then the air to be tested is forced through the solution by alter- 
nately expanding and contracting the bulb, the number of 
times required to make the solution colorless being a measure 
of the CO2. The various parts in 10,000 corresponding to the 
compressions of the bulb are as follows: 12 parts, 16 com- 
pressions; 20 parts, 8 compressions; 22 parts, 7 compressions; 
25 parts, 6 compressions; 30 parts. 5 compressions. 

28. Humidity of the Air. — Humidity is the water vapor or 
moisture mixed with the air in the atmosphere. The weight 
of water vapor a given space will hold depends entirely on the 
temperature and pressure and is entirely independent of the 
presence or absence of the air. 

The efifect of any changes of the barometric pressure upon 
the humidity are slight and may usually be disregarded. More 
time is required for the water vapor to diffuse in air than in 
a vacuum. 

Absolute Humidity is the weight of a cubic foot of water 
vapor at -a given temperature and percentage of saturation. 
It is usually expressed as grains per cubic foot. 

Relative Humidity is the ratio of the weight of water vapor 
in a given space, to the j^'cight which the same space ^ill hold 
when fully saturated at the same temperature, and is expressed 
as a percentage. The term ** Humidity '' as usually employed 
signifies relative humidity. 

Dew Point is the temperature at which saturation occurs 
for a given weight of water vapor. It is the temperature at 



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PRINCIPLES OF VENTILATION. 



37 



which any reduction in temperature would cause condensa- 
tion of some of the water vapor as dew particles. Air contain- 
ing any amoimt of moisture must have a dew point, since the 
temperature can always be lowered enough to cause conden- 
sation. 

Measurement of Humidity, — The method generally employed 
is to observe the lowering of temperature by evaporation. This 
is the difference between the temperature readings of the wet 
and dry bulb thermometers, when placed in a strong current 
of air. The thermometers used should be accurate and not 
placed too dose together, to prevent the dry bulb from being 
affected by the moist and cool air around the wet bulb. The 
wet bulb of the thermometer which gives a depressed reading 
due to evaporation should be covered with soft clean muslin 
drawn tightly over it, which is to be kept thoroughly wetted. 

Relation of Dry Bulb, Wet Bulb and Dew Point— The fol- 
lowing table shows the relative wet bulb, dry bulb and dew 
point temperatures in a sample of air if heated to the tempera- 
tures given. 



Dry Btdb. 


Wet Bulb. 


Dew Point. 


Grs. of Moisture 
per Cubic Foot. 


Relative 
Humidity or 

Per Cent 
Saturation. 


SO 
60 

70.5 
87 


SO 
S4S 
S9 
6S 


SO 
SO 
SO 
SO 


4.076 
4.076 
4.076 
4.076 


100 
70 
SO 
30 



It will be noted that there is a much smaller rise in the wet 
bulb temperature than in the dry bulb, and that the dew point 
remains constant throughout. 

The Sling Psyckromeier is probably the most accurate instru- 
ment in general use for measuring the humidity in the air. 
This instnunent consists of wet and dry bulb thermometers, 
provided with a handle, which permits of the thermometers 
being whirled rapidly. There are several forms of stationary 
wet and dry bulb hygrometers, which will give accurate results 



» HEATISG ASD %'ESTILATISG. 

if placed in a current of air. Two fotins are shown here, ( 
with an attached humidity chart so that the relative and abi 
lute humidities can be read directly without further i 




tions. In the hair hygrometer, Fig. 15, the hair increases or 
diminishes in length, in proportion to the amount of moisture 
in the air, and moves a pointer of the instrument. A scale 



PRINCIPLES OF VENTILATION. 39 

graduated by comparison with an accurate sling psychrometer 
serves to show the relative humidity of the air. This instru- 
ment is subject to a gradual deterioration and needs to have its 
accuracy checked up where any dependence is placed upon 
its indications. 

The weight of any vapor that air can possibly contain at 
various temperatures may be obtained by consulting tables 
of the properties of the vapor as for instance the Steam Tables. 
Steam Tables are principally devoted to the properties of steam 
at high temperatures although a limited number of quantities 
are given for the low temperatures. Accurate values are given 
in the Marks and Davis Steam Tables, of which an abstract is 
presented in this work. 

The degree of moisture in the air has an important influence 
on ventilation. When air is saturated with moisture water is 
deposited on all bodies which conduct heat readily and have 
a lower temperature than the air. On the other hand, if the 
air is entirely deprived of watery vapor it evaporates moisture 
from the body, and thus causes an unpleasant sensation. When 
the air is saturated no evaporation can take place from the body. 
When the air is very dry, very rapid evaporation will take place. 
A mean condition between these two extremes is required in 
every case. The air should be from 50 to 70 per cent saturated 
in order to feel pleasant, and be of the most value for ventila- 
ting purposes. The higher the temperature the more notice- 
able are either excessive moisture or excessive dryness. 

29. Measurement of the Relative Air Supply. — The air is 
vitiated mostly by high temperature and humidity. It is also 
probably vitiated by organic matter thrown off by respira- 
tion and perspiration; and the bad effects due to " close air " 
are partly due to the accompanying rise in the temperature 
and the hmnidity of the air. Since the latest researches have 
shown that a man's breathing is regulated so that the average 
CO2 content inside the lungs is from 5 to 6%,* and that air 
containing up to 2% of CO2 and otherwise pure can be breathed 

* Ency. Britannica. 



40 HEATING AND VENTILATING. 

without noticeable discomfort, it follows that the CO2 is in itself 
harmless, only acting to dilute the air and its oxygen. But 
since the CO2 in the air is the only available measure of the per- 
centage of respired air in the room, it Is used as a check on the 
amount of impurities introduced by respiration and combustion. 

It is estimated, provided that the CO2 is only introduced 
by respiration, that at each respiration of an adult person 
20 cubic inches of air on the average are required, and that 16 
to 24 respirations take place per minute; so that from 320 to 
480 cubic inches, or about one-fourth of a cubic foot, are required 
per minute.* The air is ejected from the lungs at 90 to 98®, 
is nearly saturated and contains from 3 to 5% CO2, hence is 
from I to 3% lighter than air inhaled. 

The following table shows the approximate effect of respi- 
ration on the composition of air if 

Entering Respired 
Air. Gases. 

Oxygen, per cent of volume 20. 26 16 

Nitrogen, '* '* 78.00 75 

Watery vapor * * * ' i . 70 5 

Carbonic acid ** ' * 0.04 4 

The carbon dioxide may indicate the relative amount of 
air respired. Thus if we consider that each person uses one 
quarter cubic foot of air per minute, and that the respired 
air contains 400 parts in 10,000 of carbonic acid, while the enter- 
ing air contains but 4, we can calculate the amount of air which 
must be provided to maintain any standard of purity desired. 
The formula for this operation would be as follows: If a=the 
number of parts of CO2 in 10,000, thrown out per person per 
minute in respiration; if 6 = the cubic feet of air used per minute; 
if w = the standard of purity to be preserved, expressed as the 
number of units of CO2 permissible in 10,000, and C = the 

* This is estimated by Box as 800 cubic inches, but is given by recent phys- 
iologists as above. See works of Dalton, Dr. Carpenter, Art. Respiration in 
£ncy. Brie, etc. This is increased by violent exercise, and to make the allowance 
liberal 576 cubic inches or i cubic foot is taken as the amount to be supplied. 

t Ency. Britannica, Art. Respiration. 



PRINCIPLES OF VENTILATION. 



41 



number of cubic feet of air required per person per minute — 
we shall have 

C-ab/{n—4). 

For the condition we have just considered, for each adult 
person a = 400, 6 = J, so that the formula becomes 

C=ioo/(n— 4). 

The following table shows the amoimt of air which must 
be introduced for each person in order to maintain various 
standards of purity: 



AMOUNT OF AIR REQUIRED PER PERSON FOR VARIOUS STAND- 
ARDS OF PURITY. 



Standard Parts of COs in 


Cubic Feet of Air required per Person. 


10.000 of Air in the Room. 
in) 


^er Minute. 
(C.) 


Per Hour. 
CX60 


S 


100. 


6000 


6 


50 


3000 


7 


33 


2000 


8 

• 


25 


1500 


9 


20 


1200 


10 


16.7 


1000 


II 


14 3 


857 


12 


12. 5 


750 


13 ' 


II. I 


667 


14 


10 


600 


IS 


91 


546 


16 


8.3 


500 


18 


7.1 


428 


20 


6.2 


375 



The combustion of one cubic foot of gas per hour contam- 
inates about the same amount of air as one person, so that an 
allowance, equivalent to that required for four or five people, 
should be made for each gas-burner. 

Authorities differ greatly as to the amoimt of air to be pro- 
vided per person, but at the present time they seem well united 
in considering the admission of 30 cubic feet of air per minute 



42 HEATING AND VENTILATING. 

for each person as giving good ventilation, and this amount 
is required by law for school buildings in Massachusetts, New 
York, and other states having ventilating laws. 

Some authorities insist that a higher standard should be 
required, but there is little doubt that present conditions would 
be very much improved could the above amount be obtained 
in every case. 

The supply of fresh air necessary for these standards is 
high on account of the low efficiency by which the air is dis- 
tributed. The manner in which the air is supplied to the 
occupants is of more importance than the amount of air supplied 
or the air space allowed each occupant. Air that short cir- 
cuits through the rooms without displa>dng or mingling with 
the air in the room is manifestly of little real value for venti- 
lating purposes. Five hundred cubic feet per hour well 
distributed is of more value than 4000 cubic feet per hour 
which goes through the room without coming down to the 
breathing zone. 

Air samples for carbon dioxide should be taken in the breath- 
ing zone of a room in order to show the relative purity of the 
air. If the samples are taken in the air leaving a room a low 
CO2 content may be a sign of poor distribution of the fresh 
air rather than a sign of good ventilation. If the amount of 
air supplied the room be measured and the CO2 sampled in the 
exit air, and the size of the room and the number of occupants 
known, the method given on the preceding page will give the 
relative efficiency of the air distribution by comparison of the 
results with the table on the preceding page. 

Dr. \V. A. Evans states before the A.S.H. & V.E., 191 1, 
that — " As to ventilation, is not the standard the complex 
standard of everjthing in hygiene and sanitation? For example: 
If a building is so located that it gets lots of sunshine in its 
interior, the ventilation standards can be lowered twenty per 
cent with safety to the occupants. If the ventilation is of a 
basement where sunshine cannot gfit in» then the standard 
should go twenty per cep^ m a hoqutal, 

the standard^ 1 itihegen* 



PRINCIPLES OF VENTILATION. 43 

eral health rate is lower; or, if people bearing potential infec- 
tion are jammed very close together the standard must be 
higher than where occupation is very sparce; or, if hygiene 
and cleanliness are of a very high standard the ventilation 
standard can be lowered." 

Without doubt, it is true that so far as quality is concerned 
our best standard is the external air surrounding the building 
to be ventilated. Investigation also indicates that the utili- 
zation of the external air for natural ventilation by raising 
the windows and regularly admitting the air to the apartment 
to be ventilated is desirable when the conditions are favorable. 
Generally speaking, it is not desirable to have a system of ven- 
tilation which will not permit the direct communication with 
the outside air by the opening of windows. It however must 
be recognized that no supply of a definite amount can be obtained 
by merely connecting a room with the outside air by opening 
a window, and that as a consequence a system of ventilation 
which depends alone on the opening of windows will be certain 
to fail and will be certain to give air which will differ largely 
from the external air surrounding the building. 

30. Influence of the Size of the Room on Ventilation. — The 
purity of the air of a room depends to some extent on the pro- 
portion of its cubic capacity to the number of inmates. This 
influence is often overestimated, and even in a large room if 
no fresh air be supplied the atmosphere will quickly fall below 
the standard of purity. It must be considered that no room 
is hermetically sealed. Ventilation takes place through every 
crack and cranny, and even by diffusion through the walls 
of the room. Such ventilation is generally, however, uncer- 
tain and inadequate. Large rooms have the advantage over 
small ones that they act as reservoirs of air, and also because 
there is chance for intermittent ventilation such as occurs when 
doors or windows are opened, and for the casual ventilation 
which takes place through the walls and around the windows. 
They are also advantageous, because a larger volume of air 
may be introduced with less danger of producing disagreeable 
air-currents or draughts. The following table, taken in part 



44 



HEATING AND VENTILATING. 



from article " Ventilation," Encyc. Britannica, gives a general 
idea of the cubic capacity per person usually allowed in certain 
cases, and the time which would be required to reduce the air 
inclosed to the lowest admissible standard of purity (12 parts 
of CO2 in 10,000 of air), provided no fresh air was admitted. • 



Class of Building. 



Hospitals 

Middle-class houses. . . . 

Barracks 

Good secondary schools 
London Board schools. . 
Workhouse dormitories. 
London lodging-houses . 
One-roomed houses . . . . 



Cubic Contents. 



Time required for 
Contaminating 
the Air. 




70 mm. 



59 

35 
29 

8 

18 

14 
13 



<4 
<< 
<< 
4< 
4« 



It is seen from the above table that in the ordinarj' grade 
of middle-class houses it would require about one hour to render 
the air unfit for breathing, while for the lowest grade of houses 
the time required would be only 13 minutes. It may be said, 
however, respecting the cheaper grade of houses, that while 
the amount of space allowed per person is small, the character 
of construction is such that air can usually enter or leave the 
room without very great retardation, and consequently this 
table does not fairly represent the character of ventilation 
actuallv secured. 

Pettenkofer found that, by diffusion through the walls, 
the air of a room in his house containing 2650 cubic feet was 
changed once every hour when the difference of exterior and 
interior temperatures was 34 degrees. With the same differ- 
ence of temperature, but with the addition of a good fire in a 
stove, the change rose to 3320 cubic feet per hour. With all 
the cre\'ices and openings about doors and windows pasted up 
air tight the change amounted to 1060 cubic feet per hom:; 
with a difference of 40 degrees the ventilation through the walls 
amounted to 7 cubic feet per hour for each square yard of wall 
surface. The effect of diffusion in changing the air of a room 



PRINCIPLES OF VENTILATION. 45 

should generally be neglected in practical ventilation, because 
it is very uncertain in amount and character. 

31. Force for Moving the Air. — No definite ventilation can 
be secured unless provision is made for (i) power for moving 
the air, (2) passages and inlet for admitting the air, (3) passages 
and outlet for escape of air. Air is moved for ventilating 
purposes in two ways: first, by expansion due to heating; and 
second, by mechanical means. 

The effect of heat on the air is to increase its volimie and 
lessen its density directly in proportion to the increase in absolute 
temperature. The lighter air simply because of its less density 
tends to rise, and is replaced by the colder air below. The head 
which induces the flow is a column of air corresponding in weight 
to the difference in heights of columns of equal weight of cold 
and heated air. The velocity can be computed, since theo- 
retically it will be equal to the square root of twice the force 
of gravity into this difference of height. The result so com- 
puted will apply only when there is unrestricted openings at 
both ends. It is scarcely ever applicable to chinmeys, for the 
reason that the flow of air is retarded by passing through the fuel. 

The theoretical amount of air which will pass through venti- 
lating flues of ordinary construction and of different heights is 
given in Table XVI in Appendix. 

The available force for moving the air which is obtained 
by heating is very feeble, and quite likely to be overcome by 
the wind or external causes. Thus to produce the slight pres- 
sure equivalent to one-tenth inch of water in a flue 50 feet in 
height would require a difference in temperature of 50 degrees. 
In a flue of the same height a difference of temperature of 150 
degrees would produce the same velocity as that caused by a 
pressure of 0.15 inch of water. To produce the same velocity 
as that due to a pressure sufficient to balance o.i inch of water 
will require that the product of height of chimney and differ- 
ence of temperature should be 1760. 

It will in general be found that the heat used for produc- 
ing velocity, when transformed into work in a steam-engine is 
considerably in excess of that required to produce draught by 



46 HEATING AND VENTILATING. 

mechanical means. In a rough way, an increase in temperature 
of one degree increases the head producing the velocity only 
about one part in 500. 

Ventilation by Mechanical Means is i>erformed either by 
pressure or by suction. In the first case the air is increased 
in density and discharged by mechanical force into the flue, 
the flow being produced by an excess of pressure over that of 
the atmosphere, so that the air tends to move in the direction 
of least resistance, which is outward to the atmosphere. In 
the second case, pressure in the flue is less than that of the 
atmosphere, and the velocity is produced by the flowing in of 
the outside air. By both processes of mechanical ventilation 
the air is supposed to be moved without change in temperature, 
and the force for moxTng it must be sufficient to overcome 
effects of wind or change of temperature, otherwise the intro- 
duction of air will not be positive and certain. 

32. Measurements of the Velocity of Air. — The velocity of 
air or other gases may be measured directly by an instrument 
called an anemometer, or indirectly by difference of pressure. 
The anemometer which is ordinarily employed for this purpose 
consists of a series of flat vanes attached to an axis and a series 
of dials. The revolution of the axis causes motion of the hands 
in proportion to the velocity of the air. In the form shown 
in Fig. 16 the dial mechanism can be started or stopped by a 
trip arranged conveniently to the operator. In some instances 
the dial mechanism is operated by an electric current, in which 
case it can be located at a distance from the vanes. For meas- 
uring the velocity of the wind an anemometer, which consists 
of hemispherical cups mounted on a vertical axis, is much used. 

It was shown by Mr. Combes in 1838 that if w be the num- 
ber of turns of the vane wheel and a and b constants, the velocity 
of the air would be expressed by the formula 

The pressure on any confined fluid can be expressed in any 
units desired, as pounds or ounces per square inch, or in terms 



PRINCIPLES OF VENTILATION. 



47 




Eof the height of a column of the same fluid which would give 
Ian equivalent pressure, and which is termed the kead. When 
motion takes place, a por- 
tion termed the velocity 
head is transformed into 
I velocity, while another 
Lportion, termed the prcs- 
msure head, acts to produce 
pressiire- 

The pressure head can 
3 measured by a ample 
tnanometer arranged as 
diown at A, Fig. 17, 
Vvhicb in this case con- 
lasts of a U-shaped tube 
F with one side or leg open 
and the other connected 
to a tube n opening at 
right angles to the cur- 

rnt. The manometer 
ading is equal to the difference of level ab of the liquid in the two 
legs. The head will be equal in every 
° case to the manometer reading multi- 
^ ^ " ^-V -L* P^'f^d by r, the ratio of specific weights 
[[ "V n of the manometer liquid and the air. 

The resultant velocity and pres- 
sure head can be measured by a Pilot 
tube arranged as shown at B, Fig. 17; 
this consists of a manometer connected 
to ii tube e opening to squarely face the 
moving current. The liquid in the 
manometer will balance the velocity 
head }ii=v^/2g, and also the pressure 
head. If the opening of the entering 
tube face in the opposite direction, as 
i J, the current will cause the fluid in the manometer to vary 
1 the cpposite direction, but probably by an mdefinite amount. 



— Biram'a Portable AnemofnetcT. 




48 



HEATING AND VENTILATING. 



By finding the pressure head as a.t A, and the resultant 
pressure and velocity readings as at B, we can determine by 
simple subtraction the manometer reading corre^xtnding to 
the velocity head; this multiplied by ratio of ^ledfic gravitj- r 
of the manometer liquid and the air will give the velocity head. 
From this the velocity can be computed from the formula 



By connecting one side of the manometer to the tube facing 
the current and the other to 
the tube entering at right 
angles, as shown in Fig. i8, 
the reading will show directly 
the equivalent velodty head. 
When water and dry air under 
a pressure of 29.92 inches of 
mercury- are the two fluids con- 
sidered the ratio of weights, 
r, is 773 at 52" F., 815 at 60° 
F., and 905 at 120° F., from 
which it follows that i inch of 
water would balance a column 
of dr>' air 64.5 feet high at 32° 
F.. 67.9 feet high at 60° F., 
and 75 feet high at 120° F. 
In case water is used in the manometer and the gas is air 
at a temperature of 60° r will equal 815. Hence the velocity 
V will equal 230\ //, in which A is in feet, and will equal 66.7VV 
when /;' is in inches of water. For any other temperature 
than 60 degrees this quantity must be multiplied by the square 
root of 4604-the temperature, and then dinded by V520. 
Practically for air the velocity will equal 230 times the square 
root of the difference in the heights of the columns. 

The Pilot tube should be located in a straight length of the 
air piping or passage, free of any dampers or other partial 
obstructions, with a lei^tb of at least ten diameters upstreun 




Fic. 18.— Pitol Tube. 



PEINCIPLES OF VENTILATION. 



and four diameters downstream from the Fitot tube. It is 
necessary to take a traverse across the pipe to get the accurate 
velocity, as the velocity of the air varies across the pipe from 
a variety of causes and in no regular manner, such as the eddy- 
ing and swirling of the air, the retarding of the air next to the 
walls by friction, and the distortion due to the space occupied 
by the Pitot tube. The static head does not vary appreciably 
across the pipe. To make a traverse of any shaped pipe, 
the cross-section area should be divided mathematically into 
five equal concentric areas. Then the' Pitot tube should be 
moved across the pipe taking readings in the middle pomts 
of these rings on both sides, 
giving what is sometimes 
called the ten-point method. 
Fig, 19 gives this method for 
a circular pipe. Where the 
air velocities are low the aver- 
age velocity will differ but 
little from the velocity in the 
centre of the pipre. The area 
occupied by the Pitot tube 
should be subtracted from the 
pipe area in computing the 
volume of air discharged. 
The velocity of air may also be computed by the heating 
effects, provided the amount of heat is accurately measured 
and the increase in temperature of the air be known. The 
specific heat of air is 0.2^8, hence the heat sufficient to warm 
one pound of water would heat (1/.238) =4.2 pounds of air. 
This at 60 degrees would correspond to about 55 cubic feet. 
By consulting Table X the volume heated 1 degree by i heat- 
unit at any other temperatiure can be found. 

The total number of cubic feet of air heated would be equal 
to the total number of heat-units absorbed divided by the 
number of degrees the air is heated, and this result multiplied 
by the volume of one pound divided by the specific heat (this 
computation is simplified by the use of Table X). Having 




Fig. IQ. — Ten-point Method. 



50 



HEATING AND VENTILATING. 



the total amount of air in a given time, the velocity can be 
obtained by dividing by the area of the passage. 

Note. — ^In the shape of a formula these results are as follows: Let 
T equal temperature of discharged air, / that of entering air; H equal 
the total number of heat-units given off per unit of time; V equal the 
number of cubic feet of air heated i degree by i heat-unit (see Table X) ; 
A equal area of passage in square feet; v equal velocity for the same time 
that the total number of heat-units are taken. Then we shall have 



C= Total amount of air in cu. ft.= 






C 



0^ 




Fig. 20. 



33. Calibration of the Anemometer. — The anemometer is a 
delicate instrument, not being adapted for velocities in excess 
of 1200 feet per minute, and its continued use is liable to increase 

the friction of its working 
parts and cause variation 
in the constants a and b\ 
for this reason it should 
be calibrated from time to 
time. The method usually 
prescribed for calibrating 
an anemometer is to fix 
it to a revolving arm of 
considerable length and 
swing it through still air a known number of revolutions 
corresponding to a certain distance of travel. The error of 
the instrument is determined by comparing the reading of 
the instrument with the distance passed through by the 
anemometer. Another method of calibration is by comparing 
the reading of the anemometer with air moving at a known 
velocity. The velocity of air moving through a duct of a 
given cross-section can be computed by measuring the amoimt 
of heat required to warm the air through a certain number of 
degrees, as already explained and as illustrated in the dia- 
gram Fig. 20. A duct, i4, J5, C, Z), is supplied with air by 
means of a blower located in some convenient position. A 
steam-coil is placed in one end of this duct, as at F, the ana* 



V - w «■ 



PRINCIPLES OF VENTILATION. 



51 



B 



"5 



M 




mometer to be tested is placed beyond the coil at some point, 
as m, and arranged so that successive readings may be taken 
in all portions of the cross-section; the starting and stopping 
mechanism is arranged so as to be operated from the outside 
of the box. One or more thermometers are located at TT\ 
thus permitting the measurement of the diflference in tempera- 
ture of the air. Dry steam is supplied the heater at F, and 
the water of condensation is drawn off at E, being maintained 
at a constant level by aid of the gauge-glass g. Every pound 
of steam at known pressure and quality contains an amount of 
heat which is accurately obtained from the steam-table, so 
that means are pro- 
vided for computing 
the heat-units given off. 
As this must all have 
been used in warming 
the air through a tem- 
perature r' — T, we 
have means of com- 
puting the weight, vol- 
ume, and velocity of 
air as explained. 

The constants of 
anemometers can also 
be obtained by direct 
comparison with in- 
struments having known constants and used in a similar 
manner. 

The velocity of air flowing through a duct of given size may 
also be determined by the use of large measuring-tanks which 
are alternately filled and emptied with air in such a manner 
as to give accurately the volimie of air discharged. As an 
illustration, an arrangement similar to that shown in the 
diagram, Fig. 21, could be used. F and G are two tanks like 
gasometers, which may be alternately filled and emptied, 
being raised by ropes attached to drums, D and £, which are 
operated by friction-clutches, A and B, which are thrown into 



«3P»»! 



O O Q: 

R' R' 

Fig. 21. 



V 



HMSJoa 



52 HEATING AND VENTILATING. 

action automatically and so as to raise the tanks alternately. 
R and R are rubber check-valves opening to pennit flow into 
the tanks; R' and R'y checks which open to pennit flow from the 
tanks. The volume of air discharged in a given time divided 
by the area of cross-section of the discharge duct ¥rill give the 
velocity. 

In 1884 the Prussian Mining Commission investigated, by 
means of a large gas-holder which contained over 70,000 cubic 
feet, the methods of measuring air, with the following results: 

(i)_That the anemometers calibrated by swinging in still air 
show errors which range between 7 and 13 per cent, the 
anemometers always reading high. 

(2) A Pitot tube may be used with accuracy for measur- 
ing the velocity of air, the formula being as follows: 

Velocity of air in meters per second at zero centigrade 



= 4.265 Y 



h ead of water in mm. 
density of air 

This reduced to the average temperature and density of the 

air becomes 4\^ // being the head in millimeters of water. 
The velocity in feet per second reduced to average temperature 

and density of the air becomes v = 66.yVhj h being the head 
in inches of water. 

(3) The fall in pressure between one side and the other 
of a thin orifice may be used. If H is the difference in pres- 
sure represented by feet of air, the formula for flow would be 



in which A is the area and C a coefficient which equals 0.64 
for circular orifices and 0.61 for square orifices. 

(4) The resistance due to friction as obtained in a cast- 
iron pipe 14.3 inches in diameter was found to vary as the 



PKINCIPLES OF VENTILATION. 



53 



diameter of the pipe aflfected by the exponent 1.37, as the square 
of the velocity and as the density affected by the exponent 2/3. 

The general results of the tests show that the anemometer 
gives an exaggerated value of the air discharged by a fan, 
especially when standardized by rotating in still air. In com- 
puting the volume of air delivered, the error in the result would 
be directly proportional to the error of the anemometer, which, 
as shown by the previous tests, averages not far from 10 per cent 
high. In practice the area over which velocity is to be measured 
should be divided into a number of equal parts and the 
anemometer allowed to remain in front of each part a constant 
interval of time. Twelve openings and five seconds each give 
very good satisfaction. 

34* The Effect of Heat in Producing Motion of Air. — The 
effect of heat is to expand air in 
proportion to its absolute tempera- 
ture for each degree of increase. If 
a coliunn of air be heated it will 
expand and occupy more space. In 
other words, a given bulk will have 
less weight as its temperature is 
increased; which has the effect of 
producing lack of equilibrium, and 
the warmer air will be replaced by 
colder air, causing a velocity which 

is in proportion to the change in temperature. The case is 
analogous to the action of two fluids in the branches of a 
U-tube, Fig. 22, DABC — the heavier fluid in DA and the 
lighter fluid in BC. The action of gravity causes the heavier 
fluid to flow downward and displace the lighter fluid, causing 
an upward motion in BC. If a column of the lighter fluid 
with height greater than BC balances the weight of the heavier 
fluid Z?i4, the flow which is produced will take place with a 
head equal to the difference in height of AD, and an equal 
weight of the lighter fluid. The flow ^dll take place in the same 
manner whether the heavier fluid be confined in a tube arranged 
as in the dotted lines, Fig. 22, or whether it be drawn from a 




Fig. 22. 



64 HEATING AND VENTILATING. 

large vessel, or from the surrounding air. Let the head which 
produced the draught be equal to h'y the height of the flue 
BC be A; let / be the temperatiu'e of the outside air or heavier 
fluid and if that of the lighter fluid above o°; a the coefficient 
of expansion, which for one degree of temperature of air will 
be tJt. Since the expansion is directly proportional to the 
increase in temperature, we shall have in general: 

h h^h' , . , ,, ha{i'-i) 

from which h = 



I +a/ I -^ai' I ^-at 

By substituting for a its value tJt we shall have the following for 
the head producing the flow in case air is the moving fluid: 

461(1 -f-T«iO 461 +r 

4614-/ is the absolute temperature of the air. 

The velocity is equal to the square root of twice the force of gravity, 
32.16, into the head which produces the flow, as follows: 



p.W;iA^=>-*''(^^=>^(i:^ = 8Jf-^, nearly. 

* \ I+(J/ \ 461+/ \46l-fr ^ 

The velocities given above, multiplied by 60 and by the area of cross- 
section, will give the discharge in cubic feet per minute. Mr. Alfred R. 
Wolff takes the actual discharge as 0.5 of that given by the formula, so 
that the actual discharge in cubic feet per minute would be, with 50 per 
cent allowance for friction, 



in which F equals the area of cross-section of the flue in square feet. Table 
XVI, appendix, gives the velocity in feet per second for various temper- 
atures and heights computed from the formula page 52. 

Multiplying the figures in Table XVI by 3600 gives the 
cubic feet of air discharged per hour per square foot of cross- 
section. Multiplying by 60 gives the discharge in cubic feet 
per minute, with no allowance for friction. 



PRINCIPLES OF VENTILATION. 55 

In order to find the work performed by the heat applied to moving 
the air the following calculation may be made: 

Let R equal the total heat used to warm the air in heat-units, c the 
specific heat of air (equals 0.238), T the absolute temperature = 461+/, 
P the total weight of air passing from the chimney in a given time. As 
the weight of air midtiplied by its specific heat and also by the difference 
in temperature is equal to the total heat supplied in heat-units, we have 

from which, by transposing, we have 

^=/-/) (^) 

The mechanical work in every case is to be found by multiplying the 
weight of discharge by the square of the velocity divided by twice the 
accelerating force due to gravity (2g). From a preceding formula, 

2g I 

The product of the second members of the last two equations gives 
the mechanical work in foot-pounds required to discharge the air, neglect- 
ing friction, as follows: 

2g cT 

Had the chimney been perfect, all the heat would have been converted 
into mechanical work, in which case we should have had 778 foot-pounds 
of work for every unit of heat expended, or, as a condition of perfect utili- 
zation of heat, 

Wj,= n%R (d) 

The efficiency E of the chinmey must be the quotient obtained by 
dividing equation (c) by {d) : 

^ Wa h h 



When the temperature of the outside air is 60 degrees the absolute 
temperature T is 520, and for that temperature the efficiency 

90,304 



56 HEATING AND VENTILATING. 

From this discussion it is noted that by the application of a given 
amount of beat the useful work done in discharging air from a chimney 
varies directly as the height of the chimney and inversely as the absolute 
temperature of the outside air; when the outside air is 60 degrees the 
chimney would need to be 96,304 feet in height m order to convert all the 
heat applied into useful work. 

The preceding discussion relates to the discharge of air from the chim- 
ney. The velocity of air entering the chimney will be equal to the velocity 
of discharge multiplied by the ratio of absolute temperatures of outside 
and entering air. If V represent the admission velocity, V and T the 
absolute temperatures, we shall have 






^,^.- - \2gh(T'-T) 



from which 



2g r» 



The work in foot-poimds per second will be found by multiplying 
the above value by the value of P as follows: 

„, Pr» RhT 
2g cT* 

The above equation gives the useful work performed in delivery of air 
into the chimney. The efficiency for this condition is determined by 
dividing formula (e) by formula (d)j in which case we have 

In order to utilize all the heat in the mechanical work of mox-ing the 
air, the height for this case will nce<l to be somewhat greater than for the 
preceding one. It will be noted, however, that the ciricicncy is exceed- 
ingly low for any chimney of ordinar>' height, whether we consider the 
case of supplying air to the chimney or of delivering air from the chimney. 

35. Distribution of Air.— The most difficult problem con- 
nected with ventilation is that relating to the uniform distri- 
bution of air; it is comparatively easy to introduce a definite 
volume of air into a given space in any time desired, but it is 



PRINCIPLES OF VENTILATION. 



57 



exceedingly difficult to prevent the formation of air-currents 
and eddies which interfere with efficient ventilation. The air 
for ventilation should be xmiformly distributed throughout the 
room; it also should be warmed sufficiently to prevent a sensa- 
tion of chilliness on the part of the occupants; in many instances 
all the heat needed for warming a room is obtained from the 
air for ventilation. 

It is foimd from experience that if the velocity of the enter- 
ing air is very great it produces a disagreeable current, which is 
generally known as a draught, and is more or less dangerous 
to health. The following table from Loomis' Meteorology 
gives the relation between the velocity and the sensation pro- 
duced: 



RELATION BETWEEN VELOCITY AND FORCE OF AIR. 



Sensation. 


Velocity. 


Pressure. 




Miles per Hour. 


Feet per Second. 


Lbs. per Sq. Ft. 


Tust DcrccDtible 


2 

4 
12.5 

25 

35 

45 
6o 

70 

80 

100 


2.92 

585 

18-3 
36.6 

515 
66 

88 
105 
117 
146 


0.02 


Gcntlv Dleasant 


0.08 


Pleasant brisk 


0.750 

30 

6 


Very brisk 


High wind 


Verv hieh wind 


ID 


Strone sale 


18 


Violent gale 

Hurricane 


24 
31 

49 


Most violent hurricane 



It is quite generally agreed that the velocity of the entering 
air should not exceed four to six feet per second unless it can 
be introduced in such a position as to make an insensible cur- 
rent. The table which has just been given, while only approxi- 
mately correct, gives a very fair idea of the sensations produced 
by air-currents of different velocities and pressures, and is use- 
ful in fixing limiting values. 

The most effective location for the air-inlet is probably near 
the ceiling of a room, when the height does not exceed ten or 
twelve feet. The advantages of introducing warm air at or 



58 HEATING AND \^NTILATING. 

near the top of the room are: first, the warmer air tends to rise 
and hence spreads uniformly under the ceiling; second, it 
gradually displaces other air, and the room becomes filled with 
pure air without sensible currents or draughts; third, the cooler 
air sinks to the bottom and can be taken off by a ventilating- 
shaft. So far as the system introduces air at the top of a room 
it is a forced distribution, and produces better results than other 
methods. When the inlet is placed in the floor it is a recep- 
tacle for dust from the room, and a lodging- and breeding-place 
for microbe organisms. In the ventilation of large and high 
rooms it is usually necessar>' to introduce the air at the lower 
part and discharge from the ceiling to obtain satisfactory' results. 

Some experiments were made by Mr. Warren R. Briggs, of 
Bridgeport, Conn., on the subject of the proper method of 
introducing pure air into rooms and the best location for the 
inlet and outlet. The experiments were conducted with a 
model hax-ing about one-sixth of the capacity of a schoolroom 
to which the perfected system was to be applied. The move- 
ments of the air in the model of the building were made visi- 
ble by mingling the inflowing air stream with smoke, which 
rendered all the changes undergone by it in its passage appar- 
ent to the eye. 

The results of the experiments are shown graphically in the 
six sketches. Figs. 23 to 28. In each case the distribution of 
the fresh air is indicated by the curved lines of shading. A 
study of these sketches is verj' suggestive, as it indicates the 
best results for small rooms when the inlet is on the side near 
the top, and the outlet is in the bottom and near the centre of 
the room. The tendency of the entering air to form air-currents 
or draughts, which in some instances tend to pass out without 
perfect diffusion, is well shown. This tendency is less as the 
velocity of the entering air is reduced, and we probably get. 
nearly perfect diffusion in everj- case where the outlet is well 
below that of the inlet, provided the velocity of the entering 
air is small — less than 4 feet per second. 

36. The Outlet for Air. — The outlet for air should be as 
near the bottom of a room (except in large rooms) as possible. 



PRINCIPLES OF VENTILATION. 



land it should be connected with a flue of ample size maintained 
I at a temperature higher than that of the surrounding air, unless 




Fic. as- — Air Introduced on Sidt, Discharged on Opposite Side. 



I forced circulation is in use, in which case the excess of pressure 

Kin a room will produce the required circulation. If the tempera- 

aire in a room is higher than that of the surrounding air. and 



HEATING AND VENTILATING. 



if the flue leading to the outside air can be kept from cooliog 
and is of ample size and well proportioned, the amount of air 




which will be discharj^ed will be gi\'en quite accurately by the 
taMcs referred to. Tlieae ConditiQns should lead us to locate 
\'cxit-f]ues on the insid!m|||g|d||0|lK or building, and wbfre 



PRINCIPLES OF VENTILATION. 61 

they will be kept as warm as possible by the surrounding bodies. 
If for any reason the temperature in the flue becomes lower 
than that of the surrounding air the current will move in a 
reverse direction, and the ventilation system will be obstructed. 
Vent-flues built into the sides of the chimneys are eflScient 
because they employ the waste heat from the furnace gases 
to promote the flow of the air. 

The conditions as to size of the outlet register are the same 
as those for the inlet; the register should be of ample size, the 
opening should be gradually contracted into the flue, and every 
precaution should be taken to prevent friction losses. 

37. Ventilation-flues. — ^The size of ventilation-flue will de- 
pend to a great extent upon the character of system adopted, 
but will in all cases be computed as previously explained. A 
practical system of ventilation generally is intimately con- 
nected with a system of heating, and the various problems 
relating to the size and construction of ventilating ducts will 
be considered later. In general the ducts should be of such 
an area as not to require a high velocity, since friction is to 
a great extent due to this cause. 

The size of the ventilating duct can be computed, knowing 
its rise, length, and the difference of temperature, by dividing 
the total amount to be discharged by the amount flowing through 
one square foot of area of the flue under the same conditions. 
(See Table XVI, Appendix.) 

In introducing heated air into a room, it is very much bet- 
ter to bring in a large volume heated but slightly above the 
required temperature of the room rather than a small volume 
at an excessively high temperature. If the temperature of the 
air entering be 25 degrees above that of the air in the room, 
the discharge in a flue one square foot in area would be, in 
cubic feet per second, 5.7 for a height of 10 feet, 9.0 for a height 
of 25 feet, 1 1.4 for a height of 40 feet, if no loss from friction, 
as given in Table XVI. The actual discharge can be safely 
taken as 50 to 60 per cent of the theoretical. 

As the difference of temperature of the air in the room 
and outside may usually be taken as 20°, the velocity in feet 



62 HEATING AND VENTILATING. 

per second for heights corresponding to the distance of floor 
to roof in a building of 3 stories would be about as follows: 
ist floor, 5; 2d floor, 4; attic or top floor, 3 — or about one- 
half the theoretical. For air entering, the order of the veloc- 
ities would be reversed on the particular floors. The area of 
the flue would be found by dividing the total air required per 
second by these numbers. 

38. Summary of Problems of Ventilation. — From the fore- 
going considerations it is to be noted that the practical prob- 
lems of ventilation require the introduction, first, of thirty or 
more cubic feet of air per minute for each occupant of the room, 
and in addition sufficient air to provide perfect combustion 
for gas-jets, candles, etc., which are discharging the products 
of combustion directly into the room. Second, the problem 
requires the fresh air to be introduced in such a manner as to 
make no sensible air-currents, and to be in such quantities as 
to keep the standard of contamination below a certain amount. 
This problem can be solved by either, first, moving the air 
by heat, in which case the motive force is very feeble and likely 
to be counteracted by winds and adverse conditions; second, 
by moving the air by fans or blowers, in which case the circu- 
lation is positive, and not influenced by other conditions. 

The methods for meeting these conditions will be given 
imder appropriate heads in later articles. 

It will generally be found much more convenient. to esti- 
mate the air required, not in cubic feet per minute for each 
person, but by the number of times the air in the room ¥rill 
need to be changed per hour. If the number of people who 
occupy a room be known, and each one requires 30 cubic feet 
of air per minute or 1800 cubic feet per hour, one can easily 
compute the niunber of times the air in a room must be changed 
to meet this requirement. Thus a room containing 1800 cubic 
feet, in which five people might be expected to stay, would 
need to have the air changed five times per hour in order to 
supply the required amount for ventilation purposes. 

By consulting Table X, Properties of Air, it will be seen 
that one heat-unit contains sufficient heat to warm 55 cubic 



PRINCIPLES OF VENTILATION. 63 

feet of air, at average pressures and temperatures, one degree; 
so that practically to find the number of heat-units required 
for warming the air one degree we must simply divide by 55 
the number of cubic feet to be supplied. If the cubic contents 
of the room is to be changed from five to ten times per hour, 
we can verj' readily make the necessary computations by know- 
ing the volume of the room. 

Even in the case of direct heating, where no air is purposely 
supplied for ventilation, there will be a change by diffusion of 
the air in a room that the writer has found practically met 
by an allowance equal to one to three changes in the cubic 
contents per hour. The heater must supply heat for ventila- 
tion purposes in addition to that transmitted by the walls. 

The number of times that air will need to be changed per 
minute in a given room will depend upon its size as compared 
with the niunber of occupants. If we take the smallest size 
of rooms, in which we allow only 400 cubic feet of space per 
occupant, a supply of 30 cubic feet per minute would change 
the air in this space in 13^ minutes, or at the rate of 4I times 
per hour. If 600 cubic feet are supplied per occupant, the air 
of the room would be changed once in 20 minutes, or at the 
rate of 3 times per hour. The following table may be of prac- 
tical value, as it shows the niunber of changes per hour required 
to supply each person with 30 cubic feet per minute when the 
space supplied is as given in the table* 

Space to Each Person. Number of Times Air to be 

Cubic Feet. Changed per Hour. 

100 18 

200 9 

300 6 

400 4.5 

500 3-6 

600 3 

700 2.6 

800 2.25 

900 2 



CHAPTER III. 
AMOUNT OF HEAT REQUIRED FOR WAR^^NG. 

39. Loss of Heat from Buildings. — Heat is required to supply 
the loss due to the radiation and conduction of heat from 
windows and walls, and to warm the air required for ventila- 
tion. The amount of heat required for these various purposes 
will depend largely upon the construction of the building and 
the air needed for ventilation purposes. 

This question was investigated experimentally by P6clet, 
and it also received attention from Tredgold at about the same 
time, and has been more recently investigated by the German 
Government. Peclet's investigations were carried out with 
extreme care, and reduced to general laws. He divides the 
loss into two parts: first, that from the windows; second, that 
lost by conduction through. the walls. He considers the loss 
in each case from the exterior of the wall as due in part to 
radiation and in part to convection. 

40. Loss of Heat from Windows. — The values which Pedet 
found for glass, reduced to English measures, were as follows 
(see Art. 44 for full translation): * 

LOSS PER SQUARK FOOT PER DEOREE DIFFERENCE OF TEMPER- 
.\TURE F.VHR. PER HOUR FOR WINDOWS. 



Height of Window. ! 3 ft. 3 in. 6 ft. 7 in. ; 10 ft. ■ 13 ft. 3 in. 16 ft. 3 in. 



Ix)i^s in B. T. U. per 
square iooi fXT 
degree difference 1 
of temperature. . 



0.98 



0.945 ' o 93 0.92 o 91 

I i I ■ 



*The j;cncral formula which P^det Rives as expressing; this loss is as follows: 
M=i{T—T')\K-i-K'), in which T e<iuals tcmf)eraturc of the room, d = tem- 
perature of the air, A.' = coefficient loss for radiation. A" = cocfiicient loss for con- 

♦V4 



AMOUNT OF HEAT REQUIRED FOR WARMING. 



65 



AMOUNT OF HEAT IN BRITISH THERMAL UNITS PASSING THROUGH 
WALLS PER SQUARE FOOT OF AREA PER DECREE DIFFERENCE 
OF TEMPERATURE PER HOUR. 



Thickneas, 


Single WaU. 


Wall with Air-space. 


Inches. 










Brick or Stone. 


Wood.* 


Brick or Stone. 


4 


0.43 


0.12 


0.36 


8 


0.37 


0.065 


0.30 


12 


32 


0.04S 


0.25 


i6 


0.28 


0.033 


0.21 


i8 


0.26 


0.031 


0.19 


20 


0.25 


0.03 


0.18 


24 


0.24 


0.029 


0.17 


28 


0.22 


0.027 


0.15 


32 


0.21 


0.025 


0.13 


36 


0.20 


0.020 


0.12 


40 


0.18 


0.018 

• 


O.IO 



^This experiment applies to solid wood; it is evidently of little use when 
applied to wooden buildings, since these buildings generally present so many 
opportunities for loss of heat through crevices. 

For multiple glass the above numbers are to be multiplied 
by the following coefficients: 



21 2 2 

Double -, Triple -, Quadruple -, n layers —j^. 



The coefficients given above do not differ greatly from 
unity for each square foot of single glass and two-thirds as 
much for each square foot of double glass per degree differ- 
ence of temperature. 

Mr. Alfred R. Wolff, M.E., in a recent pamphlet gives 
coefficients adopted by the German Government, as follows: 

Heat transmission in B.T.U. per square foot per hour, per 
degree difference of temperature: Single window, 1.9; single 
skylight, 1. 118; double window, 0.518; double skylight, 0.621. 

ve<^tion. K' varies with the height. K is constant, and in all cases equal to 2qi 
when the temperature is measured by a centigrade thermometer. The values 
of the coefficients K and K' were determined by cxj)eriment. 



66 HEATING AND VENTILATING. 

These coefficients are to be increased, as ex^dained in the next 
article, for exposed buildings. 

41. Loss of Heat from Walls of Buildings. — The loss of 
heat depends upon the material used, its thickness, the num- 
ber of layers, the difference of temperature between outside 
and inside surfaces, and air exposure. 

The problem is one very difficidt of theoretical solution, 
and we depend principally for our knowledge on the results of 
experiments. 

The table on the preceding page was computed from 
formulae given by P6clet and reduced to English measures by 
the writer.* 

Mr. Alfred R. Wolff, in a lecture before the Franklin Insti- 
tute,t gives coefficients for loss of heat from walls of various 
thicknesses, which he translated from and transformed into 
American units from tables prescribed by the German Govern- 
ment as follows: 

FXDR EACH SQUARE FOOT OF BRICK WALL. 



#/ o" 



ThickneM of Wall - 48 



I > I 

12 10 > 20 24 20 



I » 

»■»" *A" .**" 

32 30 40 



Loss of heat per square, 
foot per hour per degree | 
difference of temperature jO. 68 



0.46 



0.32 o. 26p 2,< 0.200. 174 jo. 15 0.1290.115 



I square foot, wooden beam, planked ( as flooring K ^o.oS$ 

over or ceiled \ as ceiling A =0 104 

I square fool, fireproof construction, j as flooring A'«o. 124 

floored over \as ceiling ^'=0.145 

I square foot, single window A' = 1 .09 

I square foot, single skylight A'= i . 1 18 

I square foot, double window A =0. 518 

I square foot, double skylight A =0.621 

I square foot, door A = 0.414 

Prof. J. H. Kinealy in a recent book, '* Formulas and 
Tables for Heating," has given a translation from the German 
work by Recknagel and Rietschel of the values adopted for 

*Af»C0(r-^)-^(2C+W, in which Q-=K-\-K\ c^thitkness, and C- 
coefficient of conduction. See Table XVH. See also Art. 44 for full explanation, 
t Lecture on Heating of Large Buildings, published in pamphlet form. 



AMOUNT OF HEAT REQUIRED FOR WARMING. 



67 



computing loss of heat from buildings, which results are some- 
what nearer the results obtained by P6clet than those given 
by Wolff. The following tables are taken from that work, the 
heat expressed in B.T.U. per square foot per hour per degree 
difference of temperature being represented by K: 



Coefficient of 
Heat4o8s. K. 



Coefficient of 
Heat-loss, K. 

Single window i .03 Doors 0.410 

Double window 0.472 Plaster 1.6 to 2.6 in. thick 0.615 

Single skylight i .090 Plaster 2.6 to 3.2 in. thick 0.492 

Double ^ylight 0.492 



LOSS OF HEAT THROUGH BRICK WALLS, BRICKS 8iX4X2 INCHES, 
LAID WITH MORTAR JOINTS | INCH THICK, 



Thickness 
of WaU. 


Outside Walls. 


Inside 
Wall. Both 

Sides 
Plastered. 


With Additional Stone Pace. 


With Air- 
space of 
a. 4 Inches 
Plastered. 


No 
Plaster. 


One Side 
Plastered. 


4 Inches 
Thick. 


8 Inches 
Thick. 


xa Inches 
Thick. 


i brick 

i\ bricks 

2 ** 

2\ " 

3 " 

ii " 
4 " 

4J " 


0.52 

.37 . 
.29 

.25 
.22 

.19 
.16 

.14 

.12 


0.49 

.36 
.28 

.24 
.21 

.18 
.16 

.14 
.12 


0.43 

•33 
.26 


0.31 

.25 
.22 

.15 


0.29 

•23 
.20 

.18 

.16 

.14 


0.26 
.21 

•19 
.17 
■15 
.13 


0.25 

.21 

.19 

.16 

.14 

•13 
.12 



LOSS OF HEAT THROUGH STONE WALLS. 



Total 

Thickness. 

Inches. 


Sandstone, 
K, 


Limestone, 
K. 


Total 

Thickness, 

Inches. 


Sandstone. 


Limestone. 
K. 


12 

16 
20 
24 
28 


0.45 

•39 

•35 

•31 
.28 


0.49 

•43 
•38 
•35 
•31 


32 
36 
40 

44 
48 


0.26 

•24 
.22 
.21 
.19 


0.28 

.26 

•24 

.23 
.21 



These coefficients are to be increased respectively as fol- 
lows, as stated by Rietschel: 

Ten per cent where the exposure is a northerly one and the winds 
are to be counted on as important factors. 



68 HEATING AND \T:STILATING. 

Ten per cent when the building is heated during the daytime only, 
and the location of the building is not an exposed one. 

Tfainy pel cent when the building is heated during the daytime only, 
and the location of the building is exposed. 

Fifty per cent when the building is heated during the winter months 
iatenniltently, with long intervab (say days or weeks) of non-heating. 

Mr. Wolfi has arranged the results in a graphical fonii(Flg. 29), 
so that the values for heat losses can be obtained by inspection. 




Fig. 2g. — WolfTs Diagram of l-oss of Heat from Wal 



In this diagram distance in horizontal direction is the 
required difference In temperature between that of the room 
and the outside air; the various diagonal lines correspond to 
the different radiating surfaces of the building, floors, ceiling, 
doors, windows, etc. The heat transmitte<I per square foot of 
surface per hour is given by the numlxirs in the vertical column. 

The German Government requires computaiions to 1» made on the 
following assumed lowest temperatures; * 

■ Lectw* *- <** VMt brfoK Fnuklin Institute. 



Air-spaces between roof 
and ceiling of rooms, 



AMOUNT OF HEAT REQUIRED FOR WARMING. 69 

External temperature 4° Fahr. 

Assumed lowest temperature of non-heated cellar 
and other portions of building permanently non- 
heated 32® 

Vestibules, corridors, etc., non-heated, and at fre- 
quent intervals in direct contact with external 

air 23*^ 

' Metal and slate roofs. . . 14^ 
Denser methods of roof- 
ing, such as brick, 
concrete, etc 23° 

As the temperature to be attained in rooms of various kinds, the Ger- 
man Government prescribes for: 

Stores and dwellings 68** Fahr. 

Halls, auditoriums, etc 64° 

Corridors, staircase, halls, etc. 54° 

Prisons, occupied by day and night 64° 

In making calculations for heat losses for buildings in 
America the minimum external temperature is usually assumed 
as zero F., and the required temperature in stores .and dwell- 
ings as 70 degrees. In many portions of the country the cor- 
ridors, staircase, halls, etc., are required to be from 65° to 68°; 
while in other portions of the country the halls are required to 
be as warm as the living-rooms. In the preceding computa- 
tions no allowance has been made for the heat carried off in 
the process of ventilation, nor for that supplied from the bodies 
of people in the room, gas, electric lights, etc. 

42. Heat Required for Purposes of Ventilation. — In addition 
to the loss of heat through walls of buildings, more or 
less heat will be carried off by the air which escapes from various 
cracks and crevices. 

By consulting Table X it will be seen that, for ordinary- 
temperatures and pressures, 55 cubic * feet of air will absorb 
one heat-unit in being warmed one degree F., and hence can 
be considered the equivalent of one pound of water. 

The heat-units required for ventilation can then be foxrnd 
by multiplying the number of cubic feet of air by the differ- 

I * This quantity varies somewhat with barometric pressure and temperature. 



70 HEATING AND VENTILATING. 

cncc of temperature between warm and outside air, and di\id- 
ing by 55,^ which is essentially the same as multijdying by 
0.02. 

43. Total Heat Required. — By referring to the values for 
heat losses given by Wolff and P6clet, it will be noted that a 
fair average value would be i heat-unit for glass and 0.25 heat- 
unit for walls per degree difference of temperature per square 
foot per hour. Usually we can neglect all inside walls, floors, 
and ceilings, and consider with sufficient accuracy only the 
cx|K)sed or outside walls. 

For direct heating of residences it seems necessary to con- 
sider the air of halls changed 3 times p>er hour, that of rooms 
on first floor 2 times per hour, and that of rooms on the upp>er 
floors once per hour, to account for changes taking place by 
difl'usion. 

U C represent cubic contents of room, W the area of ex- 
lK)sc<l wall surface, G the area of glass, n the number of times 
air is changed per hour, t the difference of temperature between 
air in room and outside, we have, as a general formula for 
heat requireil, in heat-units i>er hour, 

A = (o.02«C-fC4-iir)t. 

By representing the interchange or leakage of air by /, 
and considering this a function of the exposed surface, the 
formula for the heat rei^uired becomes 

h l[(i;\\\VM. 

I should have a value for ililTcrout conditions varying from 
ij to -», 

It Sivms uivossiiry tv> remark hero that the coefficients 
obtaim\l bv IWIct ^ an* aaurato vmiIv under the a>nditions 
ginoruing his cxjvriiuonts, A trauslativ>n irvm\ Pcclet's work 

• li v*-vubiv vVMivnix v^l ixx^nv n \\w itumlxM v>{ :;v^*x ,i:r is vh.injjed. / the 
ilitTcrxrnvx* v»t tvMujvt.iiv.iv. i tho hoai umi^ j^u Nvui:Ii;:x\M . o-o :•«.'. nearly. 



\ \ 



♦ Vr^iic sU* U V h,i'oin. r^Mx 



AMOUNT OF HEAT REQUIRED FOR WARMING. 71 

is given at the end of this chapter, which indicates that in some 
cases there is a decrease in the heat transmission per unit of 
area for increase in height, and also that the total loss of heat 
from a building is greater per unit of area when one side is 
exposed than when all sides are exposed, because of reciprocal 
radiation. Practically it is doubted that these last statements 
are often correct, because the conditions which usually apply 
are different from those assumed in his computations, but 
otherwise the results of Peclet's investigations will be found 
accurate and reliable. 

In the practical application of the formula given on the 
preceding page the author considers W as the total exposed 
wall surface, including any windows or doors which it may 
contain. This increases the amount obtained by the compu- 
tation somewhat over that required by theoretical considera- 
tions, which is desirable in view of the fact that if any errors 
are made it is better to make them in the direction of 
excess requirement than otherwise. In computing the loss of 
heat in rooms which are separated frorh unheated spaces by 
partitions, the diflference in temperature between that in the 
heated room and that in the unheated space should be con- 
sidered instead of the difference in temperature between inside 
and outside air. As an illustration, in the case of rooms with an 
attic overhead, the ceiling should be considered as exposed 
wall surface with a difference of temperature equal to that 
between the attic and the outside air; for such cases the author 
has found that the requirements are satisfied if the effect of 
the ceiling surface is considered as one-third of that of the 
outside wall surface. 

Practically there is little or no difference in the amount of 
heat required to warm a wooden or a brick building, which is 
due to the fact that air-spaces lined with heavy building-paper 
make the heat losses in the one practically as small as in the 
other. There is, however, a great difference in the amount of 
heat transmitted through the walls of different buildings, due 
to good or bad construction or to use of inferior or superior 
materials; this fact renders any elaborate formula for this 



72 HEATING AND VENTILATING. 

purpose abortive. The best that can be expected of any rule 
is agreement with the average condition. 

The author in two cases measured the loss of heat, with 
the following results:* In the first case a room on the second 
floor with exposed side and end had 246 sq. ft. of wall surface 
and 96 sq. ft. of window surface. When the air in the room 
was 28 degrees above that outside the loss was 4247 B.T.U. 
per hour, and when 27 degrees above, was 4240 B.T.U. per 
hour. To supply loss of heat by the rule stated would require 
respectively 4410 and 4253 B.T.U. per hour, the error vary- 
ing from a fraction of one per cent to nearly five per cent. 
In the second case a test was made in the N. Y. State Veter- 
inary College; this showed that to maintain the room 31 degrees 
warmer than the outside air 16,000 B.T.U. were required 
per minute, of which 39 per cent escaped in the ventilation- 
flues, and 61 per cent passed by conduction through the walls 
and windows. The building was exposed on all sides, was 
3 stories in height, had 9281 sq. ft. of glass and 31,644 sq. ft. 
of exposed wall surface. By the rule quoted the building 
loss should be 532,952 B.T.U. per hour. The actual loss by 
experiment was 9120 B.T.U. per minute or 547,200 B.T.U. per 
hour, which is within two per cent of that called for by the rule. 
In this case the building was of brick, the thickness of walls 
varied from 24 to 16 inches, and the windows had single glass. 

The above experiments, which were made on a large scale 
and on actual buildings, indicate the substantial accuracy of 
the rule quoted. 

Data regarding the number of changes of air which take place 
per hour under different conditions of direct heating in buildings 
are still very deficient. The following seems to be reliable: 

Number of Changes of Air per Hour. 

Residence heating Halls, 3; sitting-room, etc., 2; sleeping-rooms, i. 

Stores First floor, 2 to 3; second floor, i } to 2. 

Ofl'ices First floor, 2 to 2}; second floor, ij to 2. 

Churches and [lublic assembly rooms, } to 2. 
Large rooms with small exposure, | to i. 

•Transactions of American Society of Heating and Ventilating Engineers, 
vols. ill. and iv. 



AMOUNT OF HEAT REQUIRED FOR WARMING. 73 

Heat Transmission through Corrugated Iron. (A test by 
A. H. Blackburn reported in " Power " — October 29, 1913.) — 
" A modem tightly enclosed corrugated iron shop building 
required approximately 1.5 B.T.U., per square foot per hour, 
per degree difference of the inside and outside temperatures, 
figiuJng the superficial area of the corrugated iron, only. It 
was practically the same as for a single window computed for 
the actual iron surface, being 1.13 per square foot against 
1.2 used for the average window surface." 

44. P£clet's Computation of Loss of Heat through Walls and 
Windows.** 

Let M represent the quantity of heat that will traverse in a unit of 
time a plate with parallel faces, having an area of one superficial unit 
and a thickness represented by e. Let / equal the temperature of the 
plate (not the adjacent air) on one surface and /' the temperature on the 
other. Let C equal the coefl5cient of conductivity. We have 

M.'-^-'' (.) 

e 

If the body is formed of two plates in contact having a respective 
thickness of e and e' and coefficients of conductivity of C and C, and a 
temperature of d for the faces in contact, we shall have 

M = , also M = ; — , 

e e 

from which, by eliminating 0j 

M^(t-0^{-^+^) (.) 

If there are a number of plates connected in the same way, we shall 
have m a similar manner 

fee' e" e'"\ 
Af = (^— 0^1^-|-7v+7v;-l-7v7/ ) (3) 

If the temperatures of the surfaces could be exactly known, it would 
^ possible to calculate the amount of heat transmitted; but while it is 

* Translated from TraiU de la Chaleur by the author. 



74 HEATING AND VENTILATINa 

possible to measure the temperature of the air in contact with the plates, 
it is not possible to measure the actual temperatures of the surfaces of 
the plates themselves. 

Denote the temperature of the air inside an apartment by T and that 
outside by V, It is evident that heat will flow from the warm room to 
the cooler air outside, and that the inner surafce of the wall will be cooler 
than the air of the room, and the outer surface will be warmer than the 
outside air. It will be possible to obtain three values of M in terms of 
the coeflicient of conductivity C, that of radiation K, and that of convec- 
tion K\ since the amount of heat received by the inner surface is equal 
to that conducted through the wall and discharged from the outer sur- 
face. In forming these equations it is assumed that the heat transmitted 
is in every case proportional to the difference of temperature, which, 
although not quite exact, is sufficiently near for practical purposes, espe- 
cially for small differences of temperature. We have three equations 
as follows: 



by combining these equations and substituting Q=K'{'K\ we have 

m 

t'=T'+~, (5) 

CQiT-T') 
^—2CTQe (^^ 

If Qe is relatively so small with reference to 2C that it may be neglected 
in the last formula, we have 

M=\Q{T-r), (7) 

in which case the heat transmitted is independent both of the thickness 
of the material and its conductibility. As an example consider several 
plates of glass varying in thickness and with a conductivity in metric 
measures as given in various tables in this book as follows: 

C=o.75, (>=/ir-|-iC'= 2.91 -1-2.20=5.10, from which 
2C-f()«=i.So-fs.ioe. Taking e equal to the following values, we have 



AMOUNT OF HEAT REQUIRED FOR WARMING. 75 



e meters 


O.OOI 


0.002 


0.003 


0.004 


0.005 


e inches 


0.04 


0.08 


0. 12 


0.16 


0.2 


2C+0e 


1.5005 


i . 50102 


1.501503 


I . 502013 


I . 502523 



The above calculation indicates that within practical limits 2C-f-(>e 
remains constant, and that the heat transmitted through glass is inde- 
pendent of the thickness and the coefficient of conductivity. 

If, on the other hand, the coefficient of conductivity C is very small 
and the thickness t is very great, we can neglect 2C in the value of 3f , 
giving us as a consequence 

Af=^2(^ (8) 

As the value of C is never less than Q for any except the poorest con- 
ductors, such as hair felt and filamentary bodies, it is necessary to have 
the thickness e very great in order to have the conditions as above prac- 
tically realized. 

If there are two walls built in close contact and without air-space 
between them, with a temperature of x at the junction surface and a 
thickness e, «', and coefficients of conductibility C, C, we shall find as 
before several values of Jlf as follows: 

^=^T^' M= ^'^^,~^'l M=Q(7--/), M=Q(/'-r), 
from which can be obtained the following value of M in terms of T and T' : 

^^^(T-n^ (^^ 



^4) 



If there are several walls in contact without an air-space between 
them, the value of the heat transmitted would be, with notation as before, 

,,=_^(z:^n^ (^^j 



2-fe 






The foregoing computation, as stated by Peclet, applies to apartments 
in which exposed walls are not opposite to each other, it being assumed 
that heat is radiated to an exposed wall by an inner unexposed wall of 
the same temperature as the room. For the condition where ail the 



76 HEATING AND VENTILATING. 

walls are exposed the temperature of each wall will be less than that of 
the room and there will be no reciprocal radiation. In considering this 
case mathematically we shall have to substitute in the last set of equa- 
tions K* the coefficient of convection for Q^K-^-K^ since, in accord- 
ance with this hypothesis, K becomes equal to o. This hypothesis gives 
lower values than in the preceding case as will be shown by example. 

There is little doubt but that the mathematical conclusion drawn by 
Peclet follows from the hypothesis adopted, viz., that all the radiant heat 
passing through the exposed walls must be reciprocally radiated from 
the interior walls. In most modem examples of heating, however, 
radiant heat is probably supplied the outside walls from furniture and 
heaters situated in the room to such an extent as to make the actual 
amount of heat transmitted practically as much in the one case as in 
the other, and in the tables already given the condition which gives the 
greatest transfer of heat only has been considered. 

As explaining the use of the formulas we take the following example 
from Peclet. Assume a wall lo meters (32.8 ft.) in height formed of 
stone masonry, with coefficient of conductiNity C=i.7 (see first column 
Table, p. 79, slightly smaller than limestone). Coefficient of radiation 
A' = 3.60 (see Article 48, p. 85) and coefficient of convection K'—i.qd 
for a wall 10 meters high (see last formula Article 47). Assume the 
interior temperature T=is^ C. (59° F.) and the exterior temperature 
r'=6° C. (42.8° F.) as corresponding with mean conditions in Paris. 

From this ^= A' -|-A'' = 3.60 -1-1.96 = 5.56. Substituting these various 
values in equations (4), (5), and (6), and assuming different values of the 
thickness {c) as follows, we have for a single exposed wall: 

Thickness (r) meters. , .0. 10 '0.20 0.30 0,40 0.50 060 0.70 0.80 0.90 i.oo 

(finches .. J.9 79 "8 15. 7 197 2J.0 27.6 31. S 354 394 
Temperature inside face 

of wall U) (leg. (' II. IS 11.6 12 12.3 12.56 12.77 12.96 13. 1 13.2 13.3 

Temperature outside face 

of wallU') deg. C\. . 10 97 9-4 9-2 90 8.8 8.7 8.6 8.S 8.4 
Calories per Sfjuare 

meter per hour. A/.. .25-4 ^^J »Q-8 179 16.2 15.0 138 12.8 12.0 li.a 

B.T.U. pers«i.ft. perhr. 9.3 8.2 7.4 6.6 59 5-5 S.i 4-7 4.4 4. 1 

For the case when all the walls arc cxix)sed wc have: 

/ dcg. C. linsi«io face) . . 8.9 
f deg. C. (outside face). S.2 
Calories per S(]uan* 

meter per hour. .\/ . . . 1 2 
B.T.U. per sq. ft. per hr. 4.4 

For walls with air-spwces, having a tenijKTalure of x and x at the 
respective sides of the air-space, wc shall find without sensible error that 
the heat transmitted through the sfxicc is by radiation and convection, 
of whidl the coefficients are A'+A"«>(>. The heat transmitted through 



y.3 


9 7 


10 




10 


3 


10. ft 


10.8 


II .0 


II. 2 


II. 9 


8.0 


7.9 


1 ■ 


< 


1 


6 


7-5 


7.4 


7.4 


7-3 


7.3 


II. I 


10.4 


9. 


1 





I 


8.6 


8.2 


7.8 


7.4 


7.0 


41 


38 


3 





3 


3 


31 


3.0 


2.8 


2.7 


a. 6 



AMOUNT OF HEAT REQUIRED FOR WARMING. 77 

each space can be represented by Q{x—x'). The value of the heat trans- 

e I e 

mitted will be expressed by substituting — -f— in equation (g) for — . 

c y c 

Preserving the same notation, we shall have walls with two air-spaces: 

If the wails are n in number and each of the same material, it follows 
that 

^,_QiI^ 



If the construction consisted of several thin walls or parts without 
an air-space of the same total thickness of the wall with air-spaces as 
above, we should have w— i parts filling the air-spaces and n parts con- 
stituting the remaining part of the wall. By substituting in equation 
(lo) the heat transmission will be for this case: 

QjT-r) Q(T-r) 

By finding the ratio in the above equations P^clet proves that a wall 
with air-spaces 0.02 m. (.8 inch) thick, as compared with the same wall 
with the spaces filled with baked clay, transmits the following proportion 
of heat: 

Number of walls or parts of walls 2 3 4 5 10 

Proportion of heat transmitted in wall with 

air-space 0.75 0.64 0.57 0.53 0.43 

He shows that the thickness of the air-space should always be such 
that 

e is less than - 



e 



The heat transmitted through the solid walls is by conduction, that 

•through the air-space principally by radiation and convection, which latter 

quantity may under the same conditions with thick spaces be so large 



78 HEATING AND VENTILATING. 

as to overbalance the gain due to the air-space. This demonstration 
shows what has been found to be practically correct: that the less the 
radiation from the surfaces of the walls the more efficient will the air- 
spaces prove to be. 

Transmission of Heat through Glass, — As already explained in con- 
nection with equation (7), the heat transmitted through glass when one 
side only is exposed to the air can practically be represented by the 
equation 

jif=ig(r-r). 

It also follows that if x be the mean temperature of the glass, 

M^{T-x)Q, M^{x''r)Q, whence .T=i(^+n. • • (13) 

When the entire enclosure is surrounded with glass P6clet states that 
the heat transmission will be somewhat less, because of the reduction in 
the temperature of the glass due to the lack of reciprocal radiation, and 
that the following equations apply: 

A/=(r-^)A", 3/=()(jt-r), 

from which we obtain 

K'T+QT' , „ QK '(T-T') . . 

^-—Q^K' *"'^ ^^ qT^^ ^'''^ 

Peclet calculates the heat transmitted by the above formulas with 
the following results: 



Height of windows, meters i 2 3 4 5 

** *' feet 3^8 6.56 9.84 13. 1 16.4 

Value of K' (coefficient of convec- ) ^^ ^ ^^ ^^^ ^^ ^ ^^ 

tion), one exposure S 

Heat transmission per hour per de- ) ,^ ^ ^. ^ ^^ ^ ^^ ^ ..^/^ 

' I . r 2.65 2.56 2.52 2.400 2.479 

gree C. per square meter, calories. ) 

Ditto per degree F. per square foot, K ^g 0.945 0.93 0.92 0.91 

B.T.U ) 

Room surrounded with glass. 
Heat transmitted per hour per ) g. ^ ^^ 1.491.47 1.45 
degree C. per square meter, calories . ) 
Ditto per degree F. per square foot, ( ^jj^ ^^^g ^^. ^^^^ ^^^^ 

B.T.U ) 



AMOUNT OF HEAT REQUIRED FOR WARMING. 



79 



It is quite probable that the hypothesis from which the equations are 
derived when the room is entirely surrounded with glass is erroneous. 

By neglecting the thickness e in the general formula it can be shown 
that the heat transmitted by multiple glass will bear the following pro- 
Ix>rtion to that transmitted by a single thickness: 

Number of glass i 2 3 4 n 

Proportion of heat transmitted i — — — 

3 2 5 i4-» 

The following tables of the coefficients for the thermal conductivity of 
poor conductors are taken from P^clct's work and are included here for 
reference. The results will be found essentially the same as given by 
various authorities in the table in the appendix. 

CONDUCTION OF HEAT FOR ONE DEGREE DIFFERENCE OF 

TEMPERATURE PER HOUR. 



Material. 



Gray marble, fine-grained 

White marble, coarse-graihed 

Limestone, fine-grained (mean of three sample?). 
Limestone, coarse-grained (mean of two samples) 

Plaster of Paris 

Brick 

Powdered brick, coarse-grained 

Fir at right angles to the fibres 

Fir parallel with fibres 

Walnut at right angles to the fibres 

Walnut parallel with fibres 

Cork 

Glass 

Sand 

Wood ashes 

Powdered charcoal 

Powdered coke 

Cotton, raw or woven 

Paper 



Per Degree 
Cent. 



Per Square 
Meter. 

X Meter 

Thick. 

Calories. 



Per Degree 
Fahr. 



Per Square 

Foot. 

I Inch 

Thick. 

B.T.U. 



28 

22.5 

14. 8 

lo.S 

36 

S-6 

1 .1 

0.75 
1-4 



o 
I 
I 
6 
2 
o 
o 
I 
o 
o 



83 

4 
15 

.2 

5 
.65 

3 

32 

27 



The following table for coefficient of convection X, as calculated from 
the last formulai Article 47, is taken from P6clet*s work: 



80 



HEATING AND VENTILATING. 



TABLE GIVING VALUES OF K' FOR VARIOUS HEIGHTS IN METERS 

FOR A PLANE VERTICAL SURFACE. 



* 








Hei«hU. 
Meters. 


K\ 


Heights. 
Meters. 


iC'. 


O.IO 


3848 


2 


2.21 


0.20 


3.186 


3 


2.13 


0.30 


2.926 


4 


2.08 


0.40 


2.770 


5 


2.05 


0.50 


2.66 


10 


1.96 


0.60 


2.58s 


15 


1.92 


1. 00 


2.400 


20 


1.90 



Tlie table shows a decrease in the coefficient of convection with increase 
in height in a vertical wall as explained in Article 47. This decrease is 
calculated from the hypothesis that the air which is heated rises whik 
remaining in contact with the body, and for this reason has its capacity 
diminished for absorbing heat. This hypothesis is doubtless true in the 
case of absorption of heat by air-currents from radiators or heated bodies, 
but is probably considerably in error for walb of buildings, and may be 
entirely neutralized by the fact that the air against the interior wall is 
likely to be much warmer near the top, thus making an increasing tem- 
perature difference. 



CHAPTER. IV. 
HEAT GIVEN OFF FROM RADIATING SURFACES. 

45. The Heat Supplied by Radiating Surfaces. — ^The heat 
used in warming is obtained either .by directly placing a 
heated surface in the apartment, in which case the heat is said 
to be obtained by direct radiation^ or else by heating the air 
which is to be used for ventilating purposes while on passage 
to the room, in which case the heating is said to be by indi- 
rect radiation. As air is not heated appreciably by radiant 
heat, this latter term is very clearly one which is used in a 
wrong sense. In this treatise we shall use the terms direct 
heating or radiation and indirect heating. 

Direct heating is performed by locating the heated surface 
directly in the apartment. This surface may be heated by fire 
directly, as is the case with stoves and fireplaces; or it may 
receive its heat from steam or from hot water warmed in some 
other portion of the premises and conveyed in pipes. The 
general principles of warming are the same in all cases, but for 
the case of stoves the temperature is greatly in excess of that 
for steam or hot-water heating surfaces. The heat is carried 
away from the heated surface partly by radiation, in which case 
the heat passes directly in straight lines and is absorbed by 
people, furniture, and objects in the room, without warming 
up the intervening air directly, and also by particles of air coming 
in contact with the heated surface, which may be the radiating 
surface, or the people and objects in the room which have been 
warmed by radiant heat. 

The sensation caused by radiant and convected heat is quite 
different; the radiant heat has the effect of intensely heating a 
person on the side towards the source of heat, and of producing 

81 



82 HEATING AND VENTILATING. 

no wanning effect whatever on the opposite side. The heat 
which has passed oflF by convection is first utilized in wanning 
the air, and the sensation produced on any person is that of 
lower temperature-heat equably distributed. Radiant and con- 
vected heat are essentially of the same nature; in the one case 
it is received by the person directly from the source of heat, 
and at a high temperature ; in the other case it is received from 
the air, which is at a comparatively low temperature. 

The heat in passing through any metallic surface raises 
its temperature an amount which depends upon the facility 
with which heat is conducted by the body and discharged 
from the outer surface. The phenomena of the flow of heat 
through any metallic substance can be illustrated by the sketch 

in Fig. 30. If E represents the source 
of heat, and A BCD a section of a 
metallic wall surrounding, the flow of 
heat takes place into the metallic sur- 

FiG. 30. ^ ^^^^' ^^^^ through the solid metal, and 

finally through the outer surface. 

It is noted that the heat meets with three distinct classes of 
resistances: first, that due to the inner surface; second, that 
due to the thickness of the material; and third, that due to the 
outer surface. The first and third resistances are due to change 
of media, and when the material under consideration is a good 
conductor, constitute the principal portion of the resistance to 
the passage of heat. 

If the resistance on the inner surface AB is small and that 
on the outer surface CD is great, the tem{>erature of the metallic 
body will approach that of the source of heat, for the reason 
that the heat will be delivered to the surface CD faster than it 
is discharged. In this case the thickness of the material is of 
little or no importance, and the rate at which heat will pass 
depends entirely upon the rapidity with which it can be 
discharged from the outer surface. 

46. Heat Emitted by Radiation. — Heat emitted by radia- 
tion, per unit of surface and per unit of time, is independent of 
the fGna and extent qi the heated body, pro\nded there are no 



HEAT GIVEN OFF FROM RADIATING SURFACES. 83 

re-entrant surfaces which intercept the rays of radiant heat. 
The amount of heat 4)rojected from a surface of such form as 
to radiate heat equally in all directions, depends only on the 
nature of its surface, the excess of its temperature over that 
of the surrounding air, and the absolute value of its tem- 
perature. 

Du Longs law is empirical and only good through a limited 
range of temperature, but gives no practicable error in the tem- 
peratures occurring in heating buildings. 

Stefan's Law which is correct for perfect black bodies is that 
the total energy radiated is proportional to the fourth power 
of the absolute temperature. The total energy radiated from 
a hot body with an absolute temperature of T to a cold body 
of absolute temperature To, where E= the total energy 
radiated, 

E=f(T^-To^) 

where /is a constant per unit of surface. 

However, no commercial radiating surface used is a perfect 
black body, so as to give a constant coefficient with varying 
temperatures. Again the coefficients of the inside walls and 
windows of the room affect the amount of heat radiated 
back which has to be deducted from the total heat radiated 
out from the heating surface, in order to get the net amount 
of heat radiated per square foot of H. S. Also about 40 to 
60 per cent of the heat given out by a radiator is taken by the 
convection or rubbing contact of the air and strictly speaking 
is not by radiation. 

Du Longs Law. — " The rate of cooling due to radiation 
is the same for all bodies, but its absolute value varies with the 
nature of the surface." It is represented by the formula 

r = wa^(a' — i), 

in which tn represents a number depending on the nature of 
the surface of the body, a represents a constant number, which 
for the centigrade thermometer is equal to 1.0077 ^^^ ^^^ ^^^ 
Fahrenheit above 32° to 1.00196, 6 the temperature of the sur- 



84 HEATING AND VENTILATING. 

rounding air, and / the excess of temperature of the body ov^ 
that of the surrounding space. 

P6clet found that if the radiant heat be received by a dull 
surface the value of m becomes equal to a constant 124.72 
multiplied by K, a coefficient which dei>ends on the nature of 
the surface. 

The results of the experiments by Peclet accord very well 
with recent experiments made in testing radiators for steam 
and hot-water heating. For these cases either wrought or 
cast iron is used, and the difference in radiating power is 
immaterial. The construction of the ordinary form of radiator 
is such as to present very little free radiating surface, as all the 
heat which impinges from one tube on another is radiated 
back, and consequently not of use in heating the apartment 

47. Heat Remoyed by Convection (Indirect Heating). — 
The heat removed by convection is independent of the nature of 
the surface of the body and of the surrounding absolute tem- 
perature. It depends on the velocity of the moving air, and is 
thought to vary with the square root of the velocity. It also 
depends on the form and dimensions of the body and of the 
excess of temperature over that of the surrounding air. Pfidet's 
experiments were, however, made in ordinary still air, and if 
the velocity is increased it should be multiplied by factors which 
will be given later. The formulae which Peclet found as apply- 
ing to bodies of different form were as follows, the results below 
being given in heat-units per square foot per hour. 

The general formula for loss by convection is, in metric 
units. 

The values of A'' depend ui>on the form and surface of the 
body and are as follows: 

For a sphere, radius r, 

A' = 1.778-1-0.13 V. 
For a vertical cylinder, circular base, radius r, height A, 

A" = (0.726+0.0345/ \>)(2.43+o.8758v''A). 



HEAT GIVEN OFF FROM RADIATING SURFACES. 



For horizontal cylinder, radius r, 

X' = 2.058+o.o382/r. 
For vertical planes, height h, 

K' '=\.^6a,+Q.(>^,6/\^h. 

Numerical values of these various quantities are given in 
tables, Art. 48- 

48. Total Heat Emitted. Piclet's Tables.— The amount of 
heat given off by radiation and convection for various dif- 
ferences of temperature and from any surface when K or K' 
is unity is given in the first table in this article, as computed 
from Pfclet's experiments. The total heat emitted by any 
surface will be obtained by multiplying the results given in the 
first table by the factor of radiation and convection for the 
required conditions. This table is exact for the surrounding 
air at 15° centigrade or 59° Fahrenheit. 

HEAT-UNITS PER HOUR. 



R*m.T,„N. 


Ca.v. 




OS. 


Biceoe o( 


Tola! Radiation 


S?„T.? 


Total. 




Diff«tn«! 


& 




Ca 


Tq? 


B.T.U. Calories 


Sq^l. 


Csloiin 
B,.E„ 


's^t. 


Caloriei 


B.T.U. 
sTpc. 


30 
JO 
40 

140 

30O 

MO 


1 
is 

1 

306 

1 


h 

X 

18, 

is 

301 

if 

4lH 

463 

679 

J8 


0- 


3b'.bY_ 


lie;; 
1:48" 




16a II 

jfii|; 
66s;; 


It 
1 

40 a 

5S 


lii 


3S 

[40 
149 






94 K 
"1! 

It- 

It" 




34'' 

IS 

3 

3 s ;; 

I.- 

a'" 

384;; 

40» ■■ 



86 



HEATING AXD VEXTILATIKG. 



FACTOR TO DETER^nXE RADUTIOX LOSS FROM V.\RIOlS 

SURFACES. 

Value of Coefficient K. 



Polished silver 0.43 

Silvered paper. : 0.42 

Polished brass o. 258 

Gilded paper o . 23 

Red copper 0.16 

Zinc 0.24 

Tin 0.215 

Polis-hed sheet iron 0.45 

Sheet lead o. 65 

Ordinar>' sheet iron 2 . 77 

Rusty sheet iron 3 .36 

Cast iron, new 3.17 

Rusty tast iron 3 . 36 

Glas^ 2.91 

Powdered chalk $.$2 



Powdered wood 3 53 

Powdered charcoal 3 42 

Fine sand $.(}2 

00 painting 3.71 

Paper 3.71 

Soot 4 . 01 

Building stone 3 ■ ^ 

Plaster 3.60 

Wood 3 .60 

Calico 3.65 

Woollens 3 . 68 

Silk 3.71 

Water 5.31 

Oil 7 24 



N<rrE. — To find the total hcut emitted by radiation, multiply the x-alue of K 
as Kiven in the above table by the numbers corresponding to radiation due to 
difference of temiK*rature as in the preceding table. 



FACTOR TO IJKTERMINE CONVECTION LOSS FROM BODIES OF 

VARIOUS DIMENSIONS. 



Diameter. 


• 

if 


•5t 

si 

c -^ 


Vertical Cy 


►'Under. 


Hei< 


?ht in Meters 


and Feet. 




I 


h 


k h 


h 


t 
k 


h 


ill 


Meters. 


Inches. 


•5 


o.s m. 


I m. 2 zn. 


3 m. 


4 m. 


5 m. 


10 m. 






'j: 


»«• 


1.64 ft. 


3.28 ft. 6.56 ft. 


0.84 ft. 


13.12ft. 


16.4 ft. 32.8 ft. 


0.025 


0.984 


.... 


5 iM 




1 








0.05 


1.9^,8 


69 


3 59 


3 55 32 : 2.95 


2.84 


2.79 


2 73 


2.62 


0. 10 


.^04 


4 38 


2.82 


S 22 


2.9 


2.68 


2 


3/ 


2-52 


2 48 


2-38 


0. 20 


7.88 


3 08 


2.44 


V05 


2 75 


2 54 


2 


44 


2 30 


2 35 


2.26 


0.40 


15 74 


2 A3 


2.2s 


2 93 


2.65 


2 45 


2 


35 


2 30 


2 . 26 2.17 


0.(iO 


23.62 


. 


2.18 


2 88 


2 . (X> 2 . 40 


2 


31 


2.2<) 


2 22 , 2.13 


0.8 


.?i-5o 


2 . 10 


2 15 


2.85 


2-57 


2.37 


2 


28 


2 23 


2 20 2 . 1 1 


0. 10 


39 -jy 


.... 




2.83 


2 55 


2.36 


2 


26 


2 22 


2.18 2 . og 


0.16 


63.0 


« 94 


ratio -^ 


.... 


.... 






• • 


■ ■ 


■ ■ • 








20 


20 


20 


15 


>,»S 


»2 5 


20 



The following table gives the total loss from various forms 
of direct radiating surfaces in still air, calculated by Peclet's 
coefficients, slightly modified by recent experiments. 

The loss of effective surface due to rays of radiant heat imping- 
ing on hot surfaces can be approximately calculated as follows: 



HEAT GIVEN OFF FROM RADIATING SURFACES. 87 



Thus in Fig. 31, supposing pipes equally hot, occupying 
the relative positions of C and 5, 
the effective radiating surface of C 
will be diminished by that i>ortion 
of the circumference intercepted 
by the lines CD and CE. The 




Fig. 31. 



HEAT-UNITS EMITTED PER HOUR PER SQUARE FOOT FROM VARIOUS 
SURFACES, DIRECT RADIATION, STILL AIR. 



Cc 


efficient or Amount per Degree 
Difference of Temperature. 


Total] 


per Square Foot per Hour.* 


Differ- 


Horizontal Pipe. Diameter. 


Horizontal Pipe. Diamcl 


ter. 


ence of 














Tempera- ^ 


in. 


4 in. 


2 in. 


I in. 


6 in. 


4 in. 


2 in. 


I in. 




Radiator. Height. 






Radiator 


. Height. 

• 




Deg. P. Ma 
Sur 


in. 
issed 
face. 


40 in. 
Thin. 


34 in. 
Massed. 


12 in. 
Thin. 


40 in. 
Massed 
Surface. 


40 in. 
Thin. 


24 in. 
Massed. 


12 in. 
Thin. 


10 0. 


55 


0.62 


0.66 


0.85 


5 50 


6.7 


6.6 


8.5 


20 I. 


II 


1.25 


1.32 


1.72 


20.2 


24.9 


26.4 


34-4 


30 I. 


18 


1-34 


1.42 


1.84 


35 


39 7 


42.7 


55-2 


40 I 


24 


1.40 


1.48 


1.92 


49.6 


56.2 


59 


77 


50 I 


29 


1.46 


I 54 


2.01 


64- 5 


73-0 


77 


100 


60 I 


33 


I 50 


1.58 


2.06 


79 8 


90 


95 


124 


70 I 


.36 


1.54 


1.63 


2.12 


95-2 


108 


"3 


148 


80 I 


40 


1-58 


1.67 


2.18 


112 


127 


133 


173 


90 I 


43 


1.63 


1.72 


2.24 


128 


147 


153 


199 


100 I 


.47 


1.66 


1.76 


2.28 


147 


167 


175 


228 


IIO I 


•51 


1. 71 


1.80 


2.34 


166 


188 


198 


257 


120 I 


•54 


1.74 


1.84 


2 39 


184 


208 


219 


287 


130 I 


•57 


1.78 


1.88 


2.44 


203 


230 


242 


318 


140 I 


.61 


1. 81 


1. 91 


2.48 


223 


252 


266 


346 


150 I 


.64 


1.84 


1.94 


2-53 


244 


276 


291 


378 


160 I 


.66 


1.87 


1.97 


2.57 


265 


300 


316 


410 


170 I 


.69 


1. 91 


2.02 


2.62 


286 


324 


341 


443 


180 I 


.72 


1.94 


2.05 


2.65 


307 


348 


367 


475 


190 I 


.75 


1.98 


2.09 


2.71 


330 


375 


393 


512 


200 I 


.78 


2.01 


2.12 


2.76 


356 


403 


415 


552 


225 I 


.87 


2.12 


2.24 


2.91 


420 


477 


500 


650 


250 I 


•97 


2.23 


2.35 


3.06 


493 


557 


587 


762 


275 2 


.07 


2.34 


2.47 


3 22 


563 


637 


670 


872 


300 2 


.17 


2.45 


2.58 


3.37 


654 


742 


780 


1020 


325 2 


■27: 


2.55 


2.70 


350 


740 


840 


882 


1150 


3SO 2 


.37 

1 


2.67 


2.82 


3.66 


835 


945 


995 


1295 



* Re«ilts divided by zooo give approximate weight of steam condensed per hour. 



88 HEATING AND VENTILATING. 

angle DCB has for its sine DB/BC. DB is the external radius of 
the pipes, BC the distance between the centres, which is usually 
not far from two diameters. In Figs. 32, 33, and 34 the ^aded 
areas show the position of surface, by which the radiant heat 
coming from a single pipe or a single section is intercepted. 
Supposing the distance apart to be as given above, the fol- 



) 




lowing table gives the percentage of reduction m amount of 
heat transmitted due to this cause, compared with single pipe 



Nombtr o[ 


Amount of Sur- 
face ftom which 
no Rwliation 


Probable Reduc- 




Per cent. 
16 


P« cent. 
8 




4J.7 


21.3 




55 
66 

73 


27-S 

33 

36- S 




79 


39. S 



HEAT GIVEN OFF FROM RADIATING SURFACES. 89 

49* Heat Transmission Varies with Circulation. — Prof. 
A. W. Richter made a series of experiments under the general 
supervision of the author for determining the rate of trans- 
mission of heat through plates of diflFerent thickness and of 
different materials from steam to water. From these experi- 
ments it was shown that the total heat transmitted from steam 
to water was a quantity which varied with the velocity of the 
water in contact with the plate, the thickness of the plate, 
and with the difference of temperature of the steam and water. 

The following table gives the results of tests with steam at 
atmospheric pressure for sea level: 

TRANSMISSION OF HEAT, STEAM TO WATER, IN B.T.U. PER SQUARE 
FOOT PER DEGREE DIFFERENCE OF TEMPERATURE PER HOUR. 



Weight of 

Water per 

Square root 


Mild Steel, Very Smooth Surface. 
Thickness. Inches. 


Cast Iron. 
Thickness. Inches. 


per Hour. 
Pounds. 


o.oi 


o.i 


o.S 


I.O 


0.0 1 


0.1 


o.S 


1.0 


O 
lOOO 
2000 

3000 

4000 


417 
476 

536 

597 
656 


368 
422 

475 
527 
582 


242 

277 
312 

347 
383 


171 
195 

220 

245 

269 


252 
288 

324 
360 

397 


228 
261 

294 
327 
363 


164 

187 

212 
236 

259 


121 

139 
156 

174 
191 




Mild Steel. Ronsh Surface. 
Thickness. Inches. 


Brass. 
Thickness, Inches. 




0.0 1 


o.x 


o.S 


1.0 


0.01 


0.1 


OS 


1.0 



1000 
2000 
3000 

4cxx> 


416 
462 

509 

610 


368 
409 
450 
491 
532 


243 
269 

297 
324 
350 


170 

189 

208 
227 

245 


487 

557 
629 

700 

772 


427 
489 
551 
613 
675 


274 
314 

353 
393 
431 


190 
218 
246 

274 
301 



Experiments made by Adams and Gerry * show substan- 
tially the same results for the transmission of heat through iron 
or steel plates from steam to water. When, however, the hot 
mediimi was one that parted with its heat slowly, as oil or air, 



^ See Tranaactions of American Society of Heating and Ventilating Engineers, 
voL X. 



90 HEATING AND VENTILATING. 

the rate of transmission was found to vary much more rapidly 
than the difference in temperature between the two media, 
and to be practically independent of the rate of circulation of 
the cooler medium; this is doubtless explained by the fact 
that the rate of transmission was limited to the rate of delivery 
of heat from the heated body. This in the case of air or oil 
is so small as to render insignificant the extra resistance caused 
by different kinds of metals, such as cast iron or wrought iron 
of different thicknesses. 

50. Methods of Testing Radiators. — So far as the writer 
knows, no standard method has been adopted for use in the 
testing of radiators, and while numerous tests have been made 
by different engineers and experimenters, they are often not 
concordant either as to the method of testing or as to the results 
obtained. The results in the testing of radiators are greatly 
affected by small variations in temperature, by irregular air- 
currents, and by the amount of moisture contained originally 
in the steam. Obscure conditions of little apparent imi>ortance 
and often disregarded greatly influence the results. The 
heat emitted by the radiator is in all cases to be computed by 
taking the difference between that received and that discharged. 
This result is accurate, and easily obtained. This heat is 
utilized in warming the air and objects in the room, and to 
supply losses from various causes, which take place constantly; 
it is diffused so rapidly, and used in so many ways, that it is 
practically impossible to measure it, although it is, of course, 
equal to that which passes through the radiator. The radiating 
surface is almost invariably heated either by steam or by hot 
water. In the case of a steam radiator the heat received may 
be determined, by ascertaining the number of pounds of dry 
steam condensed in a given time, multiplying this by the heat 
contained in one pound of steam, and deducting from this 
product the weight of condensed water, times the heat rejected 
per pound. To make a test of this kind with accuracy requires, 
first, a knowledge of the amount of moisture contained in the 
original steam; second, the pressure of the steam or its tem- 
perature; third, an arrangement for permitting water of con- 



HEAT GIVEN OFF FROM RADIATIKG SURFACES. 



91 



densation to escape from the radiator without the loss of steam 
and means of accurately weighing this water, and also of deter- 
mining its temperature. The radiator can be located in any 
desired position in the room, on the floor, or slightly elevated 
therefrom. The tem- 
perature of the room 
during the test should 
be maintained as nearly 
constant as possible, 
and no test should be 
less than from 3 to 5 
hours in length. The 
method adopted by 
Mr. George H. Bairus 
in making a radiator 
test is shown in Fig. 35. 

A similar method adopted by the author at Sibley College, 
shown in Fig. 36, is as follows: 

First, the steam supplied to the radiator is passed through 




Fic. 35-— Radiators Arranged for Testing. 




Fig. 36. — Radiator Arranged for Testing. 

a separator and a reducing-valve to remove entrained water 
and maintain a constant pressure during any given run. 
Second, the amount of moisture in the steam is measured by 
k calorimeter, and corrections made to the result for the 



92 HEATING AND VENTILATING. 

entrained water. Third, the pressure and temperature of the 
steam in the radiator are measured by accurate gauges and 
thermometers. Fourth, the amoimt of heat passing through 
the radiator is obtained by weighing the condensed steam, 
measuring its temperature, and computing by this means the 
heat discharged. 

Fifth, the air from the radiator is eflfectually removed. 
' Large errors are caused by leaving varying amoimts of air in 
the radiator. The ordinary air-valve is often very unsatisfac- 
tory for this purpose; if used, it must be closely watched, or 
the results may be seriously affected. 

The heat supplied is computed by knowing the weight, 
the percentage of moisture, and the heat contained in one 
pound of steam. Various methods were tried for drawing off 
the condensed water; in some tests a trap was used, but better 
results were obtained by employing a water-column with gauge- 
glass and drawing off the water of condensation by hand, at 
such a rate as to maintain a constant level in the glass. To 
prevent loss by evaporation, this water needs to be received 
either into a vessel containing some cold water, or else into one 
with a tight cover, the latter being generally preferred. 

Methods of Testing Indirect Steam Radiators. — For this 
case the general methods of testing should be the same as 
those previously described, and in addition the volume of air 
which passes over the radiator should be measured; also, its 
temperature before and after passing the radiator. For 
measuring the velocity of air, the anemometer which was 
described in Chapter II is used. In measuring the velocity 
the anemometer should be moved successively to all parts 
in the section of the flue, and the average of these results 
should be used. The velocity in feet per minute multiplied 
by the area of section in square feet should give the number 
of cubic feet. The number of cubic feet of air heated can 
also be computed by dividing the heat emitted by the 
radiator by the product of specific heat of air and increase 
in temperature. 

The heat which is absorbed by the air can be computed 



HEAT GIVEN OFF FROM RADIATING SURFACES. 93 

by multiplying that required to raise one cubic foot one degree, 
as given in Table X, by the total number of cubic feet warmed 
multiplied by the increase in temperature. Fig. 37 shows 
an arrangement adopted by the author in testing indirect 
radiators, the air-supply being measured by an anemometer 
not shown. 

Testing Hot-water Radiators.— The amount of heat trans- 
mitted throi^h the surfaces of a hot-water radiator can be 
determined in either of two ways: first, by maintaining circula- 
tion at about the usual rate, measuring the temperature of the 
water before entering and after leaving the radiator; also, 
measuring or weighing the water 
transmitted. The heat transmitted 
would be equal in every case to 
the product of the weight of water, 
multiplied by the loss of temper- 
ature. In making these tests the 
same precautions as to removing 
the air from the radiator must be 
adopted as in testing steam radi- 
ators. 

These radiators can also be 
tested by filling with water at 
any desired temperature and noting 
the time required for the water 
to cool one or more degrees. In this case the iron which com- 
poses the radiator would cool the same amount, and a correc- 
tion must be added. The easier way to correct for the metal 
compo^g a radiator is to consider the weight as that of the 
water increased by that of the iron multiplied by its specific 
heat. The specific heat of wrought iron b 0.114 and that of 
cast iron o.r^o; hence for a cast-iron radiator the effect would 
be the same as though we had an additional amount of water 
equal to 0.130 times the weight of the radiator. 

In the practical operation of this test the water in the 
radiator must be kept thoroughly agitated by some sort of 
stirring device. 




94 HEATING AND VENTILATING. 

51. Measurement of Radiating Surface. — The amount 
of radiating surface is usually expressed in square feet, and 
the total surface is that which is exposed to the air, and 
includes all irregularities, metallic ornaments, etc., of the 
surface. 

Where the surface is smooth and rectangular or cylindrical 
it is easily measured, but where it is covered with irregular 
projections the measurement is a matter of some difficulty and 
uncertainty. The only practical method of measuring irregular 
surface seems to be that of dividing it up into small areas and 
measuring each one of these areas separately by using a thick 
sheet of paper or a bit of cord, and carefully pressing it into 
every portion of the surface. The sum of all the small areas 
is equivalent to the total area. 

This method is at best only approximate, and even when 
exercising the utmost care different observers are likely to differ 
three or four per cent in their results. The writer has tried 
several other methods of measuring surface, but so far without 
marked success. One method, which promised good results, 
was to cover the whole surface with a thin paint and compare 
the weights with that required for covering one square foot 
of plain surface. This method proved even more approximate 
than the other, and had to be abandoned, as the paint was not 
of equal depths on all portions of the surface. 

The total contents of the radiator in cubic feet can be easily 
determined by filling it with a weighed amount of water of a 
known temperature and dividing the result by the weight of one 
cubic foot. The volume displaced by the whole radiator can 
be determined by immersing it in a tank whose cubic contents 
can readily be measured. The difference between the cubic 
contents when the radiator is in the tank and when taken out 
is the external volume of the radiator. For this test the open- 
ings in the radiator must be tightly stopped. 

The same method applied with the radiator immersed in 
both cases; but in one case with the radiator filled with air and 
the other with water would give as a result the water displaced 



HEAT GIVEN OFF FROM RADIATING SURFACES. 95 

T)y the metal actually used in the construction, or, in other 
words, the cubic volume of the metal. This could no 
doubt be more accurately obtained by dividing the weight 
of the metal by the weight of one cubic inch or cubic foot. 
These methods give accurate means of measuring the total 
external and internal volume of the radiator, but not the 
surface. 

52, Effect of Painting Radiating Surfaces. — In the experi- 
ments of P^clet which have been given in Article 48 the effect 
of different surfaces has been fully considered. From these 
experiments it would appear in a general way that the char- 
acter of the surface affects the heat given off by radiation only, 
and not that given off by convection. In ordinary cases of 
direct radiation, because the surfaces are closely massed together, 
the radiant heat does not probably exceed on an average 40 
per cent of the total heat emitted, and is negligible in indirect 
heating. From the experiments quoted, it would appear that if 
we consider the radiant heat given off as 100 from a new surface 
of cast iron, that from wrought iron would be 87, from a surface 
coated with soot or lampblack 125, from a surface with a 
lustre like new sheet lead 20^, from a polished silver surface 
13I. These results make very much less difference, when 
applied to total heat emitted, since the total radiant heat is 
only a small portion of the whole heat given off. Calling the 
radiant heat as 40 per cent of the total, we should have the 
following numbers as representing the heat emitted from 
various surfaces: 

Cast iron, new 100 Rusty surface 102 

Wrought iron 93 Bright iron surface 72 

Dull lampblack 106 White lead, dull 106 

The writer had some experiments made in Sibley College, 
the results of which showed that the effect of painting was to 
increase the amount of heat given off. 

It was found that two coats of black asphaltum paint 
increased the amount 6 per cent, two coats of white lead 9 per 



96 HEATING AND VENTILATING. 

cent. Rough bronzing gave about the same results as black 
paint. 

On the other hand a coat of glossy white paint reduced the 
amount of heat emitted about lo per cent. 

" Recent tests by Prof. John R. Allen at the University of 
Michigan give the following relative transmission value of 
radiator paints:* 

Kind of Surface. Relative Transmission. 

Bare iron surface , i . No lustre green enamel 956 

Copper bronze .76 Terra cotta enamel i .038 

Aluminum bronze 752 Maroon glass Japan 997 

Snow white enamel i .01 White Lead Paint 987 

White zinc paint i .01 

" The effect of painting is entirely a surface effect, as the 
number of coats of painting on a radiator produce very little 
difference. The heat transmission depends entirely uix>n the 
last coat put on.'' 

Prof. C. L. Norton, Boston, Mass., reported in Transactions 
of American Society of Mechanical Engineers, 1898, that the 
heat transmitted from different surfaces was proix>rtional to 
the following numbers: 

New pipe 100 Painted glossy while 100.4 

Fair conditii>n 115 Cleaned with potash 115 

Rusty and bbck i iS Coated with cylinder oil 116 

Cleaned with caustic ix)tush 1 18 Painicil dull bbck 120.5 

Painted dull white 115 Painted glossy black xoi 

53. Results of Tests of Radiating Surface.— The results 
of the ex|XTimonts of Peolet have iKvn given quite fully, and 
they will be found to agree well with bi'^t mo^^lem tests when 
the conditions are similar. The nuliating surface ordinarily 
employevl for direct systems of steam or hot -water heating 
consists of a numbi*r of piiK^ or cv>lunms closely grouped 
together. In some instaiKvs long v\>ils or s<tio> of parallel 
rows of pijH* areomplo>i\l arr;uigv\l hv^rijontallx . but oniinarily 

• Frv^iv. "Nou-s vm IUm:»^x '^••^* \ oo.t; .1: >•!• *.n I »■>- K V"cn. published 
by the lV»rx'si;v b>^^tt»vvn:K v\»i»^:\i'!> v'^'v.l.<<^• 



Si 



a s 

5's 



HEAT GIVEN OFF FROU RADIATmo SURFACES. 97 






=-:;5i ffslsHs? ssssHIHSSasHls 






II- ^IP 









ittil 






iia 



iikf. iiy 



Am 



ipst ijiljlii--^ 



98 



HEATING ANT) VENTILATING. 



the pipes are vertical and grouped together in two to four rows. 
The usual height of radiator is 36 to 40 inches with the bottom 
placed about 3 inches from the floor, making the actual height 
of radiating surface about 3 feet. In some instances radiators 
are lower, in which case the results per unit of surface are 
considerably increased. 

The value of a radiator in which the surface is grouped so 
as to prevent the free escape of radiant heat will depend largely 
upon the effectiveness with which the air-currents strike the 
heating surfaces. There is a tendenc)' for heated air to move 
in a vertical current in contact with the radiator surface, and 
thus to keep the upper portion in a ver>' hot atmosphere, which 
has the effect of materially lessening its e&dency. The prac- 
tical effect of these restrictions is to reduce the heating power 
of radiators which are composed of a large amount of surface 
closely grouped. The following summar>' of a series of radiator 
tests made by J. H. Mills shows that with ver>' small radiators 
the results are in practical accordance with those of Peclet*s 
experiments, but as the radiators ^increase in size they fall 
off about in proportion to the loss of effective radiating 
surface. 



S'l. Ft. of Radiating 


Difference of 
Temperature. 


B.l.U. per Sq. Ft. per Hour per Degree 
Difference of Temperature. 


Surface. 


1 
P^clefs Formula. Actual. 


10 
20 

30 
40 

50 
60 


155 
150 

158 
175 
155 
165 


1.86 
1.84 
1.87 
1.92 
1.86 
1.89 


2.10 
2.08 
2.06 

I 75 

I 73 
1 .67 



The table on page 97 is abstracted from one published in 
" Warming and Ventilation of Buildings/' by J. H. Mills. 

The following table gives the abstract of a large number of 
radiator tests made under the supervision of the author:* 

• Vol. I., Transactions .\mcrican Society Heating and Ventilating Engineers. 



HEAT GIVEN OFF FROM RADIATING SURFACES. 





Dimeniioni. 


Jackion 


Sri 

Woodwaid. 


TeiH of 




Name tr Kind of Radiator. 


J* 


i i 
- t. 

il 


1 

i 




1 


P 


1 


II 


i 


"S 

1 


W. I. vertical pipei 

W. 1. v«tical EiSS. Na»n 

W^I.hot-.l«.W«te™ 


4«.iJ 
4 47.14 


3>t 
35 


00 


.;b3 

1,6^ 


.... 


i;^ 


i4e 

is 

14J 

\\ 




l-S< 

J. 01 
1.8S 


lisi 


W. I. neun. WeMern No. i 
5t«]. hot wUer. Wettern 


i;i 


Eted, lUsm. Weiteni No. i . 


1.87 

if 




^'"° 




13 


■ 48.7 
I 48.. 7 

140-1 

I 40 

1 40 

1 38.6s 
iSi.i 


371 

38 
38 

38 


.... 

89 
ISO 


1.63 

1.664 


'^ 


1.688 
1.637 

■.56s 

i.sSa 
1.4S6 


2 

'i 
1 

1! 

8. 


1 
\ 

s 


1:46 

l:s6 
1:1 


■ :ai 

il 

1.80 

1:b7 

liss 

ill 


Ror»l Union.... 

Roya: Union 

Perfwlion Steam. 

Perfeclion 

HeJsie^':::: 

Ideal Hot Wrter. 

Natiooal Steam . , 

Whittier Ei. Sur. 

Michigan Indirect 

j^nch pipe, aingle, horiaontal 



HEATING AND VENTILATING. 



TESTS OF RADIATORS WITH EXTENDED SURFACE SO AS TO FORM 
AIR-FLUES. COMP.\RED WITH PLAIN CAST-IRON RADIATORS'. 





"SKS." 


1 

1 


s 


. 


5 

e 


1t„^ 




i 


1 


I. 
fi 


i 




i 1 


ill 


I'i 


i 


"_ 


tto! a./rx.: 


; 


j; 


ii 


S7.8 J.06M! 


His 


k 


OOITOI.6J 


301 311 


A- 
B 

y 

C 

f 

If 


Do. do. do. 




e'h 


';:!, 


„.L 




°"iTO 


.^:k':s 




Ri^itor 

Do. do. do. 


r 


si'ii 


bo.l 


!::■;;; 


a:f;s 


::S 


::s:sU 




Pl»in Bnndr. 

So"!^rdo. 


■; 


si'n 


'!:;■ 


» 1 «■ 


...J,] 


ss 


i».aa>4j|i.3J 


sn;; 


I>h:i.«a9«t*di- 
DcTdc'do. ■ 


;; 


h'.:: 


:;i;ts 






Sifrt « P wi-.b 


'* 


SI 


';;. 


iiiS 


Jt^ 


o ooio.i »: 


J .., 



TEST OF R.\DL\TOR SUPPLIED WTTH Sl"PERHE.\TED STE.\M, 
SIBLEY COLLEGE. 1902. 



N==;bc .-i T«-. 
















■.i Es!«-.i< iM-*.-7- :-.:■ 


:. .-.s t 














































The abn^w table jh\'»> the iv<u'i> ,^: .i feHi--; oi carefully 
CODthictcd lesCs mailtf hy ihe suiIk^t. );i^'.r,j: ihe :v>u!t5 of sup- 



HEAT GIVEN OFF FROM RADIATING SURFACES. 101 

plying steam of different degrees of superheat to a cast-iron 
radiator containing 29.6 square feet of surface. The entering 
steam was superheated by a gas-furnace as desired. By com- 
parison of the degree of superheat with the final results it will 
be noted that the heat transmitted per degree difference of 
temperature fell off materially with increase of the degree of 
superheat. Temperature readings taken from a thermometer 
inserted immediately inside the radiator {d) indicated no 
superheat, although the small condensation warrants the 
opinion that the steam in the central portion of the radiator 
was superheated. A thermometer (e) was fastened in contact 
with the outer surface of the radiator and protected as much 
as possible from loss of heat by hair felt. This thermometer 
read about 3.5 to 5.5 degrees less than the inside one, thus 
indicating an error in that method of taking temperatures of 
a radiator surface, as it is probable that the metal was almost 
at the same temperature both inside and outside. 

The following tests made by the author on cast-iron steam- 
radiators of different dimensions are interesting as showing 
that the heat transmission is lessened by increasing the height 
or the thickness of the radiator, and increased by diminishing 
the distance between the sections or parts. 



TESTS OF CAST-IRON STEAM-RADI.^TORS WITH DIFFERENT 

DIMENSIONS. 



Number of columns. 



Thickness of radiator, inches. 



Height of radiator, inches .... 
Distance between sections, ins. 
Actual surface, square feet. . . . 
Rated surface, square feet .... 
Barometer, inches 



(a) 

(*) 
ic) 



Temperature, degrees Fakr. 

Adjacent air. degrees 

Entering steam, degrees. . . 
Condensed water, degrees. . 
Difference between steam 

and air. degrees 

Steam-pressure, absolute lbs . . . 

Quality of steam, per cent 

Steam condensed per hr.. lbs. . . 

Ditto and per sq. ft., lbs. 

Total heat radiated per hr., 
B.T.U 



Ditto and per square foot 

Ditto and per degree (actual) 

Ditto and per degree (rated) 
B.T.U 



S.12 



35 
A 

2Q.60 
30.00 

29-59 



86.75 
216.3 
216.3 

129.5 
16.01 

97 
5.77 
.195 

5390 
182 

1.405 
1.385 



7.25 



35 

42.50 
29-37 



86.27 
221 . 20 
221 . 20 

134 9 
17.60 

99 

9.81 

.245 

9320 
232 



1.733 
1.624 



3 


6 


2 


9 


10.75 


7.25 


35 

3.4 

51.73 

55.00 

28.94 


14 
3.8 

36.59 
50.00 

29.93 


36 
1.2 

49.9 
52.00 

28.94 


89.53 
222.28 
222.28 


81.77 
224.59 
224.59 


79.6 
223.7 
180.3 


132.74 
17.97 
98. 5 
12.54 
.242 


132.82 
18.79 
99 
7.92 
.217 


144. 1 

18.4 

97.9 

10.5 

.21 


11.840 
229 


7515 
207 


10,308 
207 


1.725 


1.549 


1.43 


1.622 


1. 132 


1.38 



6.5 



36 
li 

49.1 
49.5 

28.94 



79.3 
223.8 
184. 1 

144.6 

18. 5 
96.7 
12.4 

.253 

12,282 
250 

1.72 

1. 71 



102 



HEATING AND VENTILATING. 



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HEAT GIVEN OFF FROM RADIATING SURFACES. 103 

The wall radiator, which gives the highest results in the 
above series of tests, was placed about four inches from a wall 
and was about 21 inches in height by 54 inches in length. Its 
efficiency is about the same as horizontal pipe surface. 

The following table is of value as showing the relation 
between coal consumption and temperatures of water and air 
in a hot-water heating system. 



CONDITIONS OF TEMPERATURE, CIRCULATION, AND COST OF 
WARMING WITH A DIRECT WATER-HEATING APPARATUS AT 
DRAPER HALL, ABBOT ACADEMY, ANDOVER, MASS., 1890, BY 
J. H. MILLS. 



















Cost of Coal for 




Average Temperatures Fahrenheit for 24 Hours. 


24 Hours, at %6 per ton 




















of 2000 lbs. 


Date 




















X890. 












' 






I 




Outside. 


Inside. 


Flow 
Water. 


Return 
Water. 


Mean. 


Loss. 


DiflF. Air 

and 

Water. 


Lbs. Coal 
per Day. 


Per 1000 
Cu. Ft. 


Feb. 24 


36« 


71' 


187' 


ISO" 


168* 


37° 


97° 


1600 


$4.80 


8.6 mills 


•• 2S 


39 


71 


196 


162 


179 


34 


108 


1250 


3.75 


6.8 " 


•• 26 


39 


70 


183 


136 


159 


47 


89 


1550 


465 


8.4 ** 


•• 27 


40 


71 


183 


14s 


164 


38 


93 


1450 


4-35 


7.9 •• 


•• 28 


39 


69 


172 


124 


148 


48 


79 


IIOO 


3.30 


6.0 " 


Mar. I 


39 


70 


175 


153 


164 


42 


94 


1150 


3.45 


6.2 *• 


2 


26 


64 


169 


131 


150 


38 


86 


IIOO 


3.30 


6.0 ** 


•• 3 


20 


69 


188 


153 


170 


35 


lOI 


1650 


4 95 


9.0 *• 


•• 4 


21 


68 


178 


141 


159 


37 


91 


1500 


4-50 


8.1 " 


•' S 


37 


69 


181 


147 


164 


34 


95 


1400 


4.20 


7.6 " 


•• 6 


20 


66 


187 


ISO 


168 


37 


102 


1650 


4-95 


9.0 •• 


" 7 


II 


63 


191 


150 


170 


1 41 


107 


1900 


5.70 


I- cent 


•• 8 


18 


6S 


183 


14s 


164 


' 38 


99 


1850 


5.55 


I " 


•• 9 


22 


S7 


157 


138 


163 


19 


90 


1050 


3.15 


5-7 mills 


•• 10 


24 


67 


172 


135 


37 


96 


1400 


4.20 


7.6 •• 


•• II 


39 


70 


182 


144 


163 


38 


93 


1300 


3.90 


7.0 •* 


•• 12 


40 


70 


157 


127 


142 


30 


72 


900 


2.70 


5.0 '* 


•• 13 


42 


63 


157 


120 


138 


37 


75 


750 


2.25 


4.0 " 


•; 14 


40 


6S 


161 


131 


145 


28 


80 


750 


2.25 


4.0 •• 


" IS 


37 


57 


155 


125 


1 140 


30 


83 


650 


1.95 


3.5 •• 


•• 16 


34 


60 


150 


114 


1 132 


36 


72 


700 


2.10 


3.8 •• 


•• 17 


19 


61 


172 


141 


1 156 


; 31 


95 


loso 


3.15 


5.7 •• 


•• 18 


35 


6x 


156 


123 


1 139 


33 


78 


1200 


3.60 


6.5 •• 


•• 19 


2S 


61 


168 


128 


148 


40 


87 


1400 


4.20 


7.6 •• 


•• 20 


28 


63 


160 


127 


1 143 


33 


80 


1200 


3.60 


6.5 *• 


•• 21 


34 


69 


157 


127 


142 


30 


73 


900 


2.70 


5.0 •• 


" 22 


37 


67 


IS5 


125 


140 


30 


73 


900 


2.70 


5.0 '• 


" 23 


35 


67 


155 


130 


132 


1 25 


65 


600 


1.80 


3.2 •• 


•• 24 


24 


60 


156 


129 


137 


37 


77 


1200 


3.60 


6.5 " 


Average 


31' 


6S» 


170° 


136** 


153*' 


34*' 

1 


87° 


1210 


>3.74 


6.8 mills 



The building is of brick, four stories above the basement, and contains 96 sleeping- and 
study-rooms. 12 music- and 24 public-rooms; total, 132, besides basement. Contains 
SS3.000 cubic feet space; exposed wall. 17.478 square feet, and 5236 feet glass. 

The heating apparatus consists of two Mills 14-section No. 5 boilers set in battery. 
Combined fire-surface, 936 square feet, with 25 square feet of grate. Third boiler runs 
djmamo. Heating surface to boiler, i to 74. Distance from boiler to last radiator, 385 
feet. Main supply-pipe, 7 in; vertical supply-pipes, i| in.; connections to radiators. I in. 

Radiatiiijg surfaces — one hundred and forty Royal Union radiators » 5000 square feet; 
indirect Golds' pin, 450; pipe surface. 1550; total 7000. Radiating surface to »pace 
warmed, i to 79. 



104 



HEATING AND VENTILATING. 



RESULTS OF RADIATOR TEST WITH SUPERHEATED STEAM. 

Radiator No. i. 

Height, 1 8". Measured surface, 38.6 sq. ft. Least distance between sections, 

i inch. 



No. <rf 
Test. 



6 

5 

4 

7 

3 
2 

8 

I 



Pressure. 
Lbs. 



2 
2 
2 

5 

5 
10 

10 
30 



Tempera- 
ture 
Air. 

Degrees. 



71 3 
77.1 
74 o 
70.2 

75.5 
72.5 
75.8 
74 I 



Tempera- 
ture 
Steam. 
Degrees. 



217.0 
217. 1 
252.8 
239.0 

252.7 
264.7 

238.4 
274 -5 



B. T. U. 
Degree per Hour 

Superheat. ' per Sq. Pt. 
per Degree. 



o 

13 

35 83 

13 10 
24.10 

26.70 

•30 
1. 10 



48 

50 
16 

41 
23 
24 
50 
83 



Pounds of 
Steam Con' 

densed 
per Hour. 



6.25 

8.13 
7.88 

9.18 
8.38 
9.18 
9 25 
14.07 



Height, 38". 



Radiator No. 2. 

Measured surface, 49.1 sq. ft. Least distance between sections, 

i inch. 



6 


2 


73 5 


217.0 


1 



1.88 


1300 


S 


2 


80.3 


217. 1 


.13 


1.92 


"75 


4 


2 


77 


252.8 


35 83 


1. 41 


12.75 


7 


5 


73-5 


239.0 


13 10 


1-74 


14.16 


3 


5 


76.7 


252.7 


24.10 1 


I 45 


13 «2 


2 


10 


74 2 


264.7 


26.70 


1.62 


15.00 


8 


10 


77 3 


238.4 


•30 1 


1. 91 


15.16 


I 


30 


76.8 


274 5 


1 .10 


I 97 


18.94 



54. Tests of Indirect Heating Surfaces. — The tests which 
have been made on indirect heating surfaces show very great 
differences in results, varying from those given by P6clet for 
the loss due to convection alone, to results which are 8 or 10 
times as great. This difference in result is no doubt due in 
each case to the velocity of air which comes in contact with 
the surface. When the indirect radiators are not freely sup- 
plied with air, or the velocity is low, the amount of heat which 
is discharged is small; when the velocity of the air is high, the 
amount of heat taken up is proportionally greater. According 
to experiments made by the writer, the coefficient of heat 
transmission increases as the square root of the velocity of 
the air. 



HEAT GIVEN OFF FROM RADIATING SURFACES. 105 

The amount of air passing over a given surface of the radi- 
ator can be estimated quite accurately by the amount of he^-t 
given off, which we can reasonably suppose in this case to be 
all utilized in warming the air. At a temperature of about 60 
degrees, i heat-unit will warm 55 cubic feet of air i degree 
(see Table X), so that the number of cubic feet of air warmed 
is equal to 55 times the total number of heat-units given off 
from I square foot of heating surface per hour, divided by the 
difference of temperature of entering and discharge air. 

Note. — ^Let r= temperature discharge air, /'=that of entering air, 
^= total number of heat-units given off by surface, a=the number of 
square feet of surface. Then, 



Cubic feet of air per square foot heating surface = 7 



55^ 



T-Oa 



Prof. John R. Allen gives the following table in his " Notes 
on Heating and Ventilation,"* derived from the results of tests: 

HEAT LOSSES FROM INDIRECT RADIATORS. 



Cubic Feet 
of Air 

Passing per 
Sq. Ft. of 
Radiation. 


Increase in Temperature Poui 
of the Air Passing. i 


ids of Steam Con- 
densed per Sq. Ft. 


B.T.U. Transmitted per 
Sq. Ft., per Degree 
Difference in Tempera- 
ture of Air Passing 
Through Radiator and 
the Steam. 
















Standard 
Pin. 


Long St£ 
Pin. 


mdard ] 
Pin. 


-»ong 
Pin. 


Standard 
Pin. 


Long 
Pin. 


50 


147 


j 
140 


125 


15 


.80 


•95 


75 


143 


137 


17 


21 


1. 17 


1.27 


100 


140 


135 


24 


26 


I 51 


1.60 


"5 


138 


132 


295 


31 


1.85 


1.90 


150 


135 


129 


355 


36 


2.22 


2.20 


175 


132 


126 


41 


405 


2.57 


2.47 


200 


130 


123 


47 


45 


2.90 


2.72 


22$ 


127 


120 


53 


49 


3-25 


3 00 


250 


"3 


118 


585 


53 


3 60 


3 20 


275 


121 


•115 


645 


57 


3 90 


3 40 


300 


119 


112 


700 


61 


4.22 


3 60 



* Published by the ** Domestic Engineering Co." 



106 HEATING AND VENTILATINO. 

EXPERIMENTS ON INDIRECT RADIATORS.* 









!i 


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s 


II 


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1 Naraei of RadUtors. 
1 EnBinim- und D.lc of 
1 EiiKrimentt 


1 


P 


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r 


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C-B.RichMd., j Novelty . . 
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Pipe coil 

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1 iM CalBc Fert oT Air per Pool per Hour. Avenge. 


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11 fCrald-.pin... 
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IJ PipecrdL... 


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J. R. Reed. r,. Whillier.... 

C.B.Richardf. Novell/, .'.' 
187J-4- 1 G. Whillier. 


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iT^.J.Biidiri.JGoWipin'^. . 
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4it\ 6M 3.64 



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1 ■Walworth,.- 



1 soo Cubic P«it ^rf AEr po Pool p« Hour. Avtnw. 


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.7. 



• From John H. Mill*' Work on Ilea' 







HEAT GIVES OFF 


FEOM EADlATIXa SURFACES. 107 




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108 HEATING AND VENTILATING. 

The two preceding tables contain an extensive summary of 
tests of indirect radiators, abstracted from Mill's work on 
Heating and Ventilation, and are of especial interest as show- 
ing the close agreement in results, whether water or steam is 
used. The higher results in this table agree fairly well with the 
rule stated ; those for natural draft are much smaller, and approxi- 
mately equal to the square root of the velocity in feet per second. 

Chapter XV on hot blast heating contains the formulas, 
tests and charts for the convection of heat from indirect heating 
surfaces with air at high velocities and with forced draft. 

55. Conclusions from Radiator Tests. — The general results 
of radiator tests can be summed up as follows: First, that 
the values for heat transmission in recent tests of direct radia- 
tors vary greatly and dijBfer more from an average result than 
from those given by Peclet, and consequently his results can 
be used with confidence as applying to modern radiators. 
Second, the results of the test show greater diBferences in favor 
of low radiators as compared with high ones than was shown 
in the experiments of Peclet. Third, the experiments do not 
show any sensible difference for different materials used in 
radiators or for hot water or steam, provided the difference in 
temperature between the air in the room and that of the fluid 
in the radiator is the same. Fourth, the internal volume of 
radiators is of value only in lessening the friction of the fluid. 
It has no special influence on the results. Fifth, the extended 
surface radiators, or radiators in which the cast iron projects 
from the surface into the air, show large results when estimated 
on the basis of projected or plain surface, but show very small 
results when estimated on the basis of measured surf ace. 
Sixth, thin radiators, or those with a few rows of tubes, always 
show a higher efficiency than deep ones or those with numerous 
rows of tubes. Seventh, comparative tests of radiators should 
only be made between radiators of similar forms, or at least 
those which have about the same amount of surface. 

Prof. J. H. Kinealy in his work translated from the German, 
" Formulas and Tables of Heating,'' gives the total value of the 
heat in B. T. U. per square foot per hour from Rietschel as follows: 



HEAT GIVEN OFF FROM RADIATING SURFACES. 109 



Heating-surface. 



Stbam: Direct Radiation. 

Smooth pipes, vertical 

" horizontal 

Pipe coiled 

*Ca8t-iron ribbed radiators 



Stbam: Indirect Radiation. 
Pipe coiled lower.than 3 feet 3 inches. 
•' " higher than 3 feet 3 inches 
*Ca8t-iron ribbed heater lower than 

3 feet 3 inches 

^Cast-iron ribbed heater higher than 
3 feet 3 inches 

Hot Water: Direct Radiation. 

Vertical pipe radiator: one row 

•^ " two rows 



" *' over two rows. 

Smooth pipe tinder 13 feet long, verti- 
cal 

Smooth pipe under 13 feet long, hori- 
zontu 

PjpecoUed 

^Cast-iron ribbed radiators 

Hot Water: Indirect Radiation. 
Pipe coiled, under 3 ft. 3 in. high . . . 
•' " over ** ** "... 

^ast-iron ribbed heater under 3 ft. 

3 in high 

♦Cast-iron ribbed heater over 3 ft. 

3 in high 



Low Pressure. 
Below 7.5 Pounds. 



Total 

B. T. U. 

per Hour. 



a6o to 275 
275 to 295 
240 to 260 
ISO to 185 



40s 
370 



295 
280 



ISO to i6s 
140 to 155 
130 to X4S 

i6s to i8s 

i8S to 20S 

150 to i6s 

8S to no 



245 
23S 

I8S 

175 



Pounds of 

Steam 
Condensed 
per Hour. 



0.2S to 0.26 
0.26 to 0.28 
o . 23 to o . 2S 
CIS to 0.18 



0.39 
o,3S 

0.28 
0.27 



High Pressure. 
Above 7*5 Pounds. 



Total 

B. T. U. 

per Hour. 



31S to 330 
330 to 3S0 
29s to 31 S 
i8s to 220 



450 
430 



32s 
315 



1 8s to 205 
I7S to IPS 
i6s to i8s 

205 to 220 

220 to 240 
1 8s to 205 
no to 140 



30s 
29S 

23S 
220 



Pounds of 

Steam 
Condensed 
per Hour. 



0.30 to 0.31 
0.31 to 0.33 
0.27 to 0.29 
0.17 to 0.31 



0.42s 
0.41S 



0.306 
0.298 



* These cast-iron radiators have only about two-thirds the capacity of the American 
radiators. 



The amount of steam condensed in pounds per hour per 
square foot can be calculated when the heat transmission per 
degree difference of temperature per square foot is given, by 
multiplying this last quantity by the difference in temperature 
between the steam and the room and dividing this result by 
the latent heat of one pound of steam at the given pressure. 
Thus if the steam is supplied at a gauge pressure of 1.3 pounds 
(16 absolute), we find by consulting the steam- table, No. XIII 
in the Appendix, that its temperature is 216^.29, and that it 
contains 962.65 B. T. U. per pound as latent heat. With 
room 70°, difference of temperature 146°, and coefficient of 
heat transmission 1.75, the total heat transmitted per square 
foot per hour becomes 255 B. T. U. This divided by 962.62 



110 



HEATING AND VENTILATING. 



gives the condensed steam as 0.265 pound, which is about 
an average case for a cast-iron radiator. 



COEFFICIENTS OF HEAT TRANSMISSION* 

By John R. Allen, 

Professor Mechanical Engiiieering, University of Michigan. 
HEAT TRANSMISSION FROM DIRECT R.\DIATORS 



Type of Radiator 
Cast Iron. 



No. 



of Square 
Feet. 



1 column 

2 column 

3 column 

6 column 

WROUGHT IRON 

1 column 

2 column 

3 column 

4 column 

l-IX. PIPE COIL 

I pipe high 

4 pipes high 

WALL COIL (c. I.) 

Section vertical 

Section horizontal 

Section vertical 

Section horizontal 

Section vertical 

Section horizontal 



48 
48 

45 
36 

12 
42 
48 
48 



No. of Lbs. Con- 
densed per Hr. 
per Sq. Ft. 



.212 

.265 

.204 

217 

446 
286 
294 
202 



Sq. Ft. per Sec. j 

5 ' 

5 

7 

7 

9 

9 



41 
425 



Coefficient of 
Transmission. 



1.82 
1.65 

I 45 
I 35 

3 27 
2.00 

1 77 
1.27 

2.8 
2.48 

1.92 
2. II 
1.70 
1 .92 

I 77 
I 98 



HEAT TRANSMISSION THROUGH C.VST-IRON RADIATOR UNDER 
VARYING CONDITIONS OF TEMPERATURE. 



1 Difference in 


Coefficient of 


Temperature. 


Transmission. 


1 


I 56 


< 100 


1.58 


120 


1 615 


140 


1 645 


150 


I ts 


160 


I 675 


170 


1 (^0 


180 


1 705 


190 


' '' 



* Read at the third annual convention of the National District Heating 
Association, June 6-8. 1911. 



HEAT GIVEN OFF FROM RADIATING SURFACES. Ill 



EFFECT OF HUMIDITY ON THE TRANSMISSION OF HEAT THROUGH 

CAST-IRON RADIATOR. 



Percentage of Mois- 


Coefficient of 


ture Saturation 


Transmission. 


20 


I 79 


30 




77 


40 




73 


50 




72 


60 




69 


70 




66 


80 




63 


00 




61 


100 




59 

1 



56. Temperature Produced in a Room by a given Amotmt 
of Surface when Outside Temperature is High. — Guarantees 
are often made respecting heating apparatus that it shall be 
sufficient to maintain a temperature of 70 degrees when the 
external air is at some fixed point, as zero, or 10 below. As 
under the exact conditions of the guarantee the trial can only 
be made when the external temperature corresponds with that 
specified, it becomes of some importance to establish an 
equivalent temperature which would indicate the efficiency 
of the heating apparatus for any specified condition. The 
following method is applicable for such computations and is 
expressed in the shape of a formula: 

Let T equal temperature of radiator, /' that of room, and / 
that of outside air for the conditions corresponding to the 
guarantee. Let B equal loss from room for i degree difference 
of temperature; let c equal the heat-units from i square foot 
of radiator per i degree difference of temperature for con- 
ditions corresponding to the guarantee; let c' denote the same 
values for other conditions; let x equal resulting temperature 
of room, /" outside air for the actual conditions, R equal square 
feet of radiation. 

For guaranteed conditions, 



(t'-t)B = c(T-OR. 



(i) 



112 



HEATING AND VENTILATING. 



(2) 



(3) 



For actual conditions, 

ix-t")B=c'iT-x)R 

Dividing (i) by (2), 

t'-t c(T-t') 

x-t"~c'{T-xy 

When I'-jo, r=220, /=o, and c = i.8, we have 

The coefficient of heat transmission c' grows less as the tem- 
perature in the room becomes higher, as abready shown in Art. 
48; so the equations can only be solved in an approximate 
manner. The following table gives the temperatures in colimin 







TABLE* 






Temperature 
Outside Air. 


Coefficient, t 

Heat per Sauare 

Foot per Hour 

per Degree. 


ToUl Heat per 

Square Foot 

per Hour. 


Resulting 

Temperature 

of Room. 


Difference 

Tempermtiore 

Radiator mad 

Room. 


10 


1.85 


288 


64.7 


155 3 





1.8 


270 


70 


150 


10 


I 75 


253 


751 


144.9 


20 


17 


236 


81 


139 


30 


I 65 


218 


86.5 


133 S 


• 40 


1.6 


203 


93 I 


128.0 


50 


I 55 


188 


98.7 


122.5 


60 


15 


172 


104.7 


116. s 


70 


I 45 


158 


no. 5 


109. s 


80 


14 


142 


117. 1 


102.9 


90 


1-35 


130.5 


123.5 


96. S 


100 


13 


117 


130 3 


89 7 



Example Showing Application of Table. — To determine by a test of the appa- 
ratus, when weather is 60**, whether a guarantee to heat to 70** in zero weather 
is maintained, operate the apparatus as though in regular use and note the average 
temperature of the room. If the room has a temperature equal to or in excess 
of 104.7** F-. it would have a temperature of 70** in zero weather, all other con- 
ditions, such as wind. [x>sition of windows, etc., being the same as on the day 
of the test. 

* This table, although calculated for steam with radiator at temperature of 
220** F., is practically correct for hot- water radiation or for steam at any pressure 
and temperature. 

t Vahie of c' in fonnube. 



HEAT GIVEN OFF FROM RADIATING SURFACES. 113 

4, which a room would have for various temperatures outside, 
provided there was sufficient radiating surface to heat the room 
to 70 degrees in zero weather. The temperature of the radiator 
in all cases is assumed to be that due to 3 pounds pressure of 
steam by gauge, or 220 degrees. 

57. Correcting for the Wind Velocity.— W. H. Whitten 
in a paper read before the American Society of Heating and Venti- 
lating Engineers, gives the following rule for correcting the 
outside temperature used for the effect of the velocity of the 
wind. "From 40 to 15 degrees above zero, i mile of wind 
movement per hour is equal to i degree drop in temperature; 
from 15 degrees plus to 20 degrees minus, i mile of wind move- 
ment per hour is equal to 1.15 degrees drop in temperature. 
This is for buildings constructed in the ordinary manner, that 
is, without protected windows. 

" This not only applies to the sides having the so-called 
greatest exposure, but, owing to the suction or nonpressure 
existing on the sheltered sides, should be applied to all sides 
of the building. 

Where the windows are equipped with efficient weather 
strips the loss of heat caused by the wind is much less. 

$8. Protection of Main Pipe from Loss of Heat. — The 
loss of heat which takes place from an uncovered main steam or 
hot-water pipe is, because of its isolated position, considerably 
greater than that which takes place from an equal amount of 
radiating surface. Unless this heat is actually required it will 
cause an expenditure of fuel the cost of which is likely to be 
in a few seasons many times that of a good covering. 

The heat lost per square foot of surface from a small 
uncovered pipe is from 375 to 400 heat-units per square foot per 
hour in steam-heating, or an amount equal to that required 
for the evaporation of 0.4 pound of steam. Computing this 
loss for ICG square feet for a day of 20 hours and for a season 
of 150 days, it will be found equivalent to the coal required to 
evaporate 120,000 pounds of steam; this would not be less 
than 12,000 pounds of coal, which at $5.00 per ton would cost 
$30.00. The cost per square foot per annum will be found on 



114 HEATING AND VENTILATING. 

the above basis to be 30 cents, of which 75 to 80 per cent would 
have been saved by using the best covering. The loss from 
hot-water pipes would be about two-thirds of the above. 

The best insulating substance known is air confined in minute 
particles or cells, so that heat cannot be removed by convec- 
tion. No covering can equal or surpass that of perfectly still 
and stagnant air; and the value of most insulating substances 
depends upon the power of holding minute quantities in such 
a manner that circulation cannot take place. The best known 
insulating substance is a covering of hair felt, wool, or eider- 
down, each of which, however, k open to the objection that, if 
kept a long time in a confined atmosphere and at a temperature 
of 150 degrees or above, it becomes brittle and partly loses 
its insulating power. 

A covering made by wrapping three or more layers of 
asbestos paper, each about ^ inch thick, on the pipe, cover- 
ing with a layer of hair felt f inch in thickness, and wrap- 
ping the whole with canvas or paper, k much used. This 
covering has an effective life of about 5 years on high-pressure 
steam-pipes and 10 to 15 years on low-temperature pipes. 
There are a large number of coverings regularly manufactured 
for use, in such a form that they can be easily applied or 
removed if desired. There k a ver>' great difference in the 
x'alue of these coverings; some of them are ver}' hea\y and 
a^ntain a large amount of mineral matter with little confined 
air, and are ver\- p^^K^r insulators. Some are composed entirely 
of ina>mbustible matter and are nearlv as good insulators as 
hair fell. In general the value of a covering is inversely pro- 
jx^rtional to its weight— the lighter the covering the better its 
insulating prv>^XTtios; other things being ev]ual. the incombus- 
tible mineral substances are tv^ be preierrevi to combustible 
material. The following table gives the results of some actual 
tests of ditTerx*nt cvnerincs. whkh \ver\* conductevi with great 
care anvi on a surnoiouriv Lir^v >c,i!c to cli'v.ir.j.tt' >*-ii:ht errors of 
observation, h\ i:v::ior;i! who :hivkv.v^< o: :hc coverings tested 
was I ir.v: h So '■** : 0^ : < \\ c re *" ,u! .* w - : -^ .;,- \ e r. n ^rs o i different 
thiv:kiu*ss<*s. tr\>'v. which i: wv>v.\* j.p-.v.i- "Z'^a: the inin in 



HEAT GIVEN OFF FROM RADIATING SURFACES. 115 

insulating power obtained by increasing the thickness is very 
slight compared with the increase in cost. If the material is a 
good conductor its heat-insulating power is lessened rather 
than diminished by increasing the thickness beyond a certain 
point. 

PERCENTAGE OF HEAT TRANSMITTED BY VARIOUS PIPE-COVER- 
INGS, FROM TESTS MADE AT SIBLEY COLLEGE, CORNELL 
UNIVERSITY, AND AT MICHIGAN UNIVERSITY.* 

Relative Amount 
Kind of Covering. of Heat 

Transmitted. 

Naked pipe loo. 

Two layers asbestos paper, i in. hair felt, and canvas cover 15.2 

Two layers asbestos paper, i in. hair felt, canvas cover, wrapped with manilla 

paper 15. 

Two layers asbestos paper, i in. hair felt 17. 

Hair felt sectional covering, asbestos lined 18.6 

One thickness asbestos board 59 , 4 

Four thicknesses asbestos paper 50.3 

Two layers asbestos paper 77.7 

Wool felt, asbestos lined 23 . i 

Wool felt with air spaces, asbestos lined 19.7 

Wool felt, plaster paris lined 25.9 

Asbestos molded, mbced with plaster paris 31.8 

Asbestos felted, pure long fibre 20. i 

Asbestos and sponge 18.8 

Asbestos and wool felt 20 . 8 

Magnesia, moulded, applied in plastic condition 22.4 

Magnesia, sectional 18.8 

Mineral wool, sectional 19.3 

Rock wool, fibrous 20. 3 

Rock wool, felted 20 . 9 

Fossil meal, moulded, J inch thick 29 . 7 

Pipe (tainted with black asphaltum 105 5 

P^ painted with light drab lead paint 108 . 7 

Glossy white paint 95.0 

Two layers wood (J") separated by paper, lined with bright tin, and coated 

outside with asphaltum 16 to 18 

* These tests agree remarkably well with a series made by Prof. M. E. Coolcy 
of Michigan University, and also with some made by G.M. Brill, Syracuse, X. Y., 
and reported in Transactions of the American Society of Mechanical Engineers, 
vol. xvi. 



116 



HEATING AND VENTILATING. 



TESTS OF PIPE COVERING MADE IN SIBLEY 

COLLEGE LABORATORY 

Tests of Ultro and Magnesia Coverings 

Size of pipe, 6 inches. Length, 50 feet in the case of bare 
pipe and Magnesia covered pipe, and 41 feet in case of Ultro 
covered pipe. The Ultro covering was composed principally 
of infusorial earth. 

Tests made in the open with the same pipe on different 
days, weather conditions as nearly identical as could be judged. 
Temperatures were observed by nine thermometers located at 
equal intervals on either side of the pipe. Over magnesia 
covering were placed one thickness of building paper and one 
thickness of 10 ounce canvas. Over the Ultro covering were 
placed three thicknesses of building paper and one thickness 
of 10 oz. canvas. 

table of results. 



Length of pipe, feet 

Radiating surface 

Thickness of covering, inches, 
over all 

Wt. of covering per ft., lbs. . . 

Steam pressure, absolute, lbs. . . 

Steam quality 

Temp, steam, deg. F. avc 

Temp, air around pipe 

Temp, air, external 

Temp, difference, air and steam 

Temp, exterior of covering 

Wt. cond. steam, dry, per hr.,lbs. 

B.T.U. radiated jxt lb. steam, 
dr>' 

B.T.U. radiated i>cr hour 

B.T.U. radiated i>er dc^. diff.. of 
temp., air and steam, per hour 
by collector 

B.T.U. radiated per dcg. diff. of 
temp, air and steam, per hr., 
net 

B.T.U. radiated per deg. diff. of 
temp, air and steam per hour 
per square foot. 

Relative 



Bare Pipe. 



49 3 
88.01 

0.0 



75 U 

99 4 
307.0 

83-7 



223 3 

63 • 78 

898.6 
57312.7 

1.6 
255.0 



Magnesia. 



2.9 



49 
88 

I 

3 
75 
99 
307 
87 
79 

2 2Q 

139 
9 

808 
8594 



01 

2 

38 

14 

7 

65 
28 

o 

37 

4 

57 

02 
05 



1.6 

35-9 

.408 
14.1 



Ultro. 



40.1 
71.91 

2.7 

9 36 
82.57 

99 o 

76.31 
78.0 

236.99 

122.8 

6.H 

894.0 
5462^.34 



1.6 

21.5 

.299 
10.3 



HEAT GIVEN OFF FROM RADIATING SURFACES. 



117 



The following table translated from P^clet's Traitf de la 
ChdeuT gives in a general way the amount of heat transmitted 
through coverings of various kinds and of different thicknesses; 
the loss from a naked pipe is t^ken as lOo: 



LOSS OF HEAT THROUGH VARIOUS PIPE-COVERINGS. 



i 


Thickn™, in inchr,. 










1 


0-4 


... 


..» 


t.a 


... 


4.. 


... 


-,..., c..„„. 


1 


.^.„^.„.... 




OOI 


M 


30 


ifl 


n 




7 


t\ 


EidM down, loose wiwl, hair felt, eK. 




OR 










30 




[l 


Powdered ihorcoal. 




i6 


sc 


4li 


41 


IK 


?^ 






W ood across 6bres. 






fifi 


l-l 


ft7 


sM 


<1 


44 


41 


Sand. 




64 


!l 


T1 


71 


7J 




70 


()» 


Clayey carLh. 




t* 


77 


*!l 


KS 


o; 


oo 




100 


Stone, rock. 


9 





7S 


a7 










1 10 


White marble. 


s 


OOJ 


W 


oo 


IS 




loo 


149 


iHo 


Solid gtts carbon. 



59. P^ Coverings. — For the insulation of the pipe many 
Toethods have been adopted, of which we may mention first 
the wooden tube and concentric air-space surroimding the 
pipe, Fig. 38. The tube is usually made by sawing out the 
interior portion of a log, leaving a shell or wall about two inches 
thick. Each length is provided with a mortise and tenon 
jcont, and the different lengths are joined together by driving. 
These wooden tubes are slipped over the steam-pipe as it is 
laid, the pipe being held in a central position by collars, so as 
to leave an air-space about one inch thick surrounding the pipe. 
Tliis pipe is usually strongly banded with hoop-iron, and the 
Jonts can be made water-tight when laid, but checks soon form 
in the wood-pipe and make crevices through which the soil- 
water can reach the steam-pipe. Recently a form of tube 
made of two layers of inch board separated by tarred felting 
has cone into use and is in general to be preferred to the solid 



118 HEATING AND VESTILATIXG. 

tube as having superior insulating qualities. A view of such 

tubing partly in section is shown in Fig. 39. 

The wooden-tube system of insulation is objectionable. 

principally because it does not protect the pipe from ground- 
water, its durability, as 
pro\'ed by experience, is 
not great, and leaks in 
the steam-pipe are very 
difficult to locate and 
repair. A modified plan 
of the construction de- 




FlG. 38.— Pipe with Wooden-tube tnsuUUon. 



scribed has been employed, in which both steam- and return- 
pipes were covered with asbestos and hair felt and placed in 
a box made of 2-inch plank; the box was laid on a concrete 
bottom three inches thick, and after the pipes were laid 
it was completely surrounded with concrete. This was 
arranged so that the steam-pipes would not be disturbed 
by decay of the wood. The concrete would in that event 
support the steam-pipes and constitute a protecting tube. The 
heat insulation proved on trial to be much superior to that of 
the sohd wooden tube, while its cost was somewhat less. 
Similar constructions in 
which the wooden tube has 
been replaced by sewer-pipe 
are in use and are of superior 
durability. In one case 
familiar to the writer a 
wooden tube lined with 
sewer-pipe was laid outside 
the steam-pipe, the whole 
being covered with earth; 
such a construction replaced 
tice its heat-insulation properties ha\e not pro\ed to be better. 

The best system of transmitting steam King distances, but 
probably also the most expensive, is to be obtained by building 
a conduit lined with brick or masonry laid in cement and 
sufficiently large for inspection and repairs. The pipe should 




— WjcUolI Built-up Wood 
Tubing. 



c shown in Fig. ^8, but ii 



HEAT GIVEN OFF FROM RADIATING SURFACES. 119 



be carried in it on proper hangers and thoroughly wrapped with 
insulating material. 

60. Tests of Pipe Coverings. 

.TESTS OF WYCKOFF WOOD PIPE COVERING 

Made in Sibley College Laboratories. 

Duration of nin, 2, hrs. Barom., 29.37 in. Size of pipe, ij in. Length of Pipe, 

100 ft. Radiating Surface, 56.2 sq. ft. 



Bare 


Covered 


Pipe. 


Pipe. 


633 


(>3-3 


100. 


100. 


296.0 


296.0 


87.0 


84.0 


209.0 


212.0 


288.0 


103.0 


95 8 


16.8 


95 8 


16.8 


906.7 


906.7 


34745 


6093 


34411 


5754 


164.6 


27.1 


2 93 


.48 


100. 


16.4 



Steam pressure, absolute 

Quality of steam 

Temperature of steam, deg. F 

Temperature of air, deg. F 

Temperature difference, air and steam 

Temperature, exterior of i)ipe covering 

Weight of condensed steam, actual, lbs 

Weight of condensed steam, per hour, dr>-, lbs 

B.T.U. radiated per lb. steam 

B.T.U. radiated per hour 

B.T.U. radiated by pipe, net 

B.T.U. per deg. diff. temp., air and steam, per hour 

B.T.U. per deg. diff. temp., air and steam, per hour, per 

sq.ft 

Relative amount of heat transmitted 



Professor Allen gives costs on piping tunnels of $7.00 and 
$9.00 per foot. One pipe covering catalogue gives prices of 
$1.00 per foot for 4-inch pipe and S2.00 per foot for a 12-inch 
pipe, for high pressure steam, and 20 per cent less cost for low 
pressure steam or hot water. 

61. Transmission of Steam Long Distances. — The loss 
of heat from systems protected by a simple wooden tube is 
considerable, rising in many cases to from 30 to 40 per cent 
of that from the bare pipe. This is, however, due to the poor 
system of insulation used, since it should not exceed in any 
case 20 per cent of that from naked pipe. The loss from the 
underground system of piping at Cornell University, which is 
somewhat over one-half mile in length, and in which the steam- 
pipes are laid inside of sewer-pipe, with a wooden tube outside 
the sewer pipe, the whole covered with about 4 feet of earth, 



120 HEATING AND VENTILATING. 

causes the consumption of about two and one-half tons of 
coal per day, which is about lo per cent of the total coal con- 
sumption when the plant is working at normal capacity. This 
heat loss is very nearly a constant amount and cannot be 
expressed as a fixed percentage of the total steam used, for 
the reason that when the steam consimiption is large this per- 
centage of loss is small and vice versa. 

High-pressure steam for power purposes is also sometimes 
transmitted in this manner and engines operated at a great 
distance from the boiler-plant. The losses from such a system 
of transmission are often serious, especially if a long pipe-line 
has to be kept hot, and if the engine is operated only a part of 
the time or only at partial capacity. Where the engine is 
worked to its full capacity, the loss is not usually large in pro- 
portion to the total transmitted. The following paragraph 
gives a careful estimate, based on actual experiment, of the 
loss experienced in transmitting constant power by various 
methods a distance of looo feet. 

The loss in transmitting power by any system is principally 
constant, and hence when the power is greatly increased the 
percentage is correspondingly reduced. The following estimate 
is based on the transmission of lOO horse-power looo feet: 

Method of Transmission. Percentage 

of Loss. 

Line shafting: 

Loss by friction (average 32) 25 to 40 

Electricity: 

Loss in transforming from mechanical to electrical, 

and vice versa 20 to 30 

Line loss 2 to 5 

Total loss, electrical transmission 22 to 35 

Convejang steam : 

Naked steam-pipe (still air) 37 to 45 

Pipe covered ^-ith solid wood and earth 1 1 to 13 

For operating machiner}' which is required occasionally or at 
intervals electricity is no doubt the most economical mediimi, 
since when the demand for power ceases the expenditure on 



HEAT GIVEN OFF FROM RADIATING SURFACES. 121 

account of transmission also becomes nothing, which is rarely 
the case either with line-shafting or steam. 



it lAo ■ Bit. H Bl>;l< ' ) Du a 1 nd Lr lin [ 


Mfln. / \ |-^/, 


m,u. f \ I 


MM ... 1 \ '■O »' Hi- l™ P* f 'j U«tl o^ .JJ « lb" 


-. / ^-."-^ / Y""^ -^ ^ 


— ^/ \T "^ —■ 










~~ ~" ' "" 


ill- L' ^^^ 




«,b." Ui fit^^^t ,^ :^1:^:^^" 


7/ 1 l^r-^fFr c\ #^-"5 


u '/ -'*•=- t' f ^ \\ 3o'^a" 


-'^ -^ \:-. , -tird^_^^-f \ -K-rnf? 




^^))>%^ A \ ^ ^ 


_ $^§ ^--z- : ,.i?^$ 


^^^/^^^ . sj-^^^ 


•it. ^ y t ^?^5' 




in N- - ^ ** ** 




^ 1 imp* tJr« f .n| n> Room ^ 


— - - ' 






Jf-L^ _ 


6' = Tm^tu^Mr^ ^ 


'*/--_.^v ■^ 


» ^ ,^sz c ^-^ 




« ' y i / 




ll.,!.™ ..14. 8,,!..!.. - 


* i<--.^^^ =^^--N __^^^--~ 





Fig. 40.— IMagnm Showing Results of Test to Determine Heat-loss in Under- 
ground Pipe. 

The diagram, Fig. 40, gives the summary of the results of 
a test of the Lehigh Coal-storage Plant, South Plainfield, N. J., ^ 



122 HEATING AND VENTILATING. 

made by the writer to detennine the heat lost in supplying 
an engine situated 740 feet from a boiler-house, the connecting 
pipe-line consisting of 250 feet of 6-inch, 106 feet of S-inch, 
and 391 feet of 4-inch pipe, having a total radiating surface of 
1057.5 square feet. 

The engine was 12-inch diameter, 16-inch stroke, running 
with a piston speed of about 600 feet a minute, thus producing, 
when cutting off at one-third stroke, a velocity \)f steam of 
about 60 feet per second in the 4-inch supply-pipe. 

The general method of testing gave the total amoimt of steam 
used, and the fall in pressure between the boilers and engine. 
The amoimt of water in the steam was determined by a throt- 
tling calorimeter at both ends, the sample of steam being drawn 
in each case from a vertical pipe located close to a bend from a 
horizontal, and collected by a half-inch nipple extending past 
the centre of the vertical pipe. The drip was caught at places 
which had been provided in the pipe, and was weighed from time 
to time. 

The barometer readings were taken with an aneroid which 
had been compared with a mercurial barometer. The cor- 
rected readings are given in the summary' as well as in the 
diagram. Simultaneous observ^ations were taken everj*- ten 
minutes. A study of the summar}*^ shows that the loss was 
sensibly constant during the run. This is clearly shown by 
noting the fact that any increase in the amount of steam flowing 
through the line had the effect of decreasing the percentage of 
moisture at the engine. 

The total heat loss per hour was 72,322 B.T.U. The 
average steam -pressure was 70.1 pounds by gauge, its tempera- 
ture 313.6° F., and the average outside temperature 16.6° F. 
The loss for each degree difference of temperature between 
that of outside air and that of steam was 243.7 B.T.U. per 
hour. The loss. in B.T.U. per square foot per hour was 0.229 
per degree difference of temperature. 

This for a difference of temperature of 150 degrees cor- 
responds to an amount about 10 per cent of that which would 
have been given off from a naked pii)e. 



nEAT GIVEN OFF FROM RADIATING SURFACES. 123 

The loss by condensation varied from 3 to 8 per cent, the 
loss of pressure and consequent ability to do work about 6 per 
cent. The total loss was not far from 10 per cent from both 
these causes; if this had been proportional to length, it would 
have been 13.5 per cent for a line iocx> feet in length. 

The diagram shows variations in the observed quantities 
as they occurred from time to time. It is to be noted that as 
the demand for steam at the engine was large the moisture in 
the steam delivered was correspondingly reduced. 



CHAPTER V. 
FLOW OF WATER, STEAM AND AIR 

62. Flow of Water and Steam. — It seems necessary to 
say a few words respecting the general laws which apply before 
considering the practical application. The velocity with 
which water flows in a pipe is computed from the same general 
laws as those appl>*ing to the fall of bodies. The velocity is 
produced, however, not by actually falling through a given 
distance, but by a difference of pressure, which must be expressed, 
not in {X)unds per square inch, but in feet of head. This head 
is in ever\' case to be found by inultiplying the difference of 
pressure by the height required for the given fluid to make one 
pound of pressure. If we denote by h the difference of head 
as described, by g the force of gravity =3 2. 16, by v the velocity 
in feet per second, we would have in case of no friction 



r = \ 2gh, 

The quantity discharged per second would be found in 
e\'ery case by multipl>'ing the velocity by the area of the orifice 
in square feet. 

In the flow of water in pipes there is considerable friction, 
which acts to reduce the velocity and the amount discharged; 
this increases with the length and decreases with the diameter 
of the pipe. 

The friction caused by bends and by passing through 
valves and into entrance of pipes is of considerable amount, 
and often requires consideration. It can be considered as 
producing the same resistance to flow as though the pipe had 
been increased in length certain distances as follows: 90-degree 
elbow is equivalent to increase in length of the pipe 52 diam- 

124 



FLOW OF WATER, STEAM AND AIR. 125 

eters, globe-valve 70 diameters, entrance of a pipe in tee or 
elbow 60 diameters, entrance in straight coupling 20 diameters. 

The flow of steam in pipes presents some problems slightly 
different from that of flow of air, but in many respects the 
two cases are similar. There is a tendency for the steam to 
condense, which changes the volume flowing and affects the 
results greatly. The effect of condensation and friction is to 
reduce the pressure in the pipe an amount proportional to the 
velocity and also to the distance, and these losses are greater as 
* the pipe is smaller. There are at the present time exact data 
regarding the steady flow of steam in pipes, yet it has been cus- 
tomary for writers to assume that the same laws which apply 
to the flow of water hold true for steam also, and that the same 
methods can be used in computing quantities. These results 
are certainly safe, although no doubt giving sizes somewhat 
larger than strictly necessary for the purposes required. 

In estimating the size of steam-pipe for power purposes it 
is customary to figure the area of cross-section, such as giving 
a velocity of flow not exceeding 100 feet per second. This 
velocity is generally accompanied by a reduction of pressure 
in a straight pipe of about one pound in 100 feet. For steam- 
heating purposes the general practice is to use a much larger 
pipe and lower velocity, so that the total reduction in pressure 
on the whole system is much less; the effect of a drop in pres- 
sure of one pound will cause the water to stand in the return- 
pipe in a gravity system 2.4 feet above the water-level in the 
boiler. 

63. Gravity Hot Water. — The velocity of water and steam 
in a gravity system of heating is due to a different cause from 
that in the case just considered, for the reason that the pres- 
sure up)on the heater acts uniformly in all directions, and exerts 
the same force to prevent the flow into the boiler from the return, 
as to produce the flow into the main. For such cases the sole 
cause of circulation must be the difference in weight of the 
heated bodies, hot water, or steam, in the ascending column 
axid the cooler and heavier body in the descending column. 
The velocity induced by a given force will be reduced in propor- 



126 



HEATING AND VENTILATING. 



tion as the acting force is less. In the case of steam-heating 
the difference between the weight in the ascending and descend- 
ing column is so great that the velocity will not be 
essentially diflferent from that of free fall, provided 
correction is made for loss of head due to fric- 
tion, etc., as explained, but in case of hot water 
the theoretical velocity produced will be found very 
small. 

The case is analogous to the well-known problem 
in mechanics in which two bodies A and B of un- 
equal weights are connected by a cord passing over 
the frictionless pulley C (Fig. 41). 




The heavier body B in its descent draws up the lighter 
body A, In this case the moving force is to the force of 
gravity as the difiference in the weights is to the sum of the 
weights, and the velocity is the square root of twice the 
force into the height. 
In other words, if / equals the moving force, we have by proportion 

f : g::B-A : B-hA, 



Fig. 41. 



from which 



f-i 



B-A 



which, substituted in place of / in formula 
v=y/ 2fhy gives the following as the velocity: 



■4 



2g(B-A)h 



B-\-A ' 

h being the height fallen through. 

In applying this to the case of hot-water 
heating we have, instead of the descent and 
ascent of two solids of different weights, the 
descent and ascent of columns of water connected 
as shown in Fig. 42, the heated water rising in the 
branch AF and the cooler water descending in 
the branch BC. The force which produces the 
motion is the difference in weight of water in 
the two columns; the quantity moved is the 
sum of the weight of water in both columns. 

This is equal to the difference in weight of i cubic foot of the heated 
and cooled water divided by the sum, multiplied by the total height of 




lI:^ 



• 1 11 1 i 



Fic. 42. — Cifiulation 
fl«)l-water Pipe. 



in 



FLOW OF WATER, STEAM AND AIR. 



127 



water in the system, so that if Wi represents the weight of i cubic foot 
in the column BC, and W represents the weight of i cubic foot in the 
column AFy and h represents the total height of the system, then the 
velocity of circulation will, be, in feet per second. 



^-4 



2gh(Wi-W) 



iWx-\-W) 



In this formula no allowance whatever is made for friction, 
consequently the results obtained by its use will be much in 
excess of that actually found in pipes. The amoimt of fric- 
tion will depend upon the length of pipe and its diameter. 
As result of experiment the writer foimd considerable variation 
in different measurements of velocity, but in no case did he 
find a velocity greater than that indicated by the formula. 
The following table is calculated from the formula without 
allowance for loss by friction. The computation is made with 
the colder water at i6o degrees F., although little difference 
would be found in calculations at other temperatures. 

VELOCITY IN FEET PER SECOND IN HOT-WATER PIPES. 



Height or 


: Free Fall 
in Air. 




S*' 


Difference 
10° 


of Temperature. 






Head in 
Fee^ 


i« 


IS** 


i 20<» 


300 


4o<> 


I 


8.03 


0.107 


0.242 


0.335 


0.412 


0.478 


0.593 


0.672 


5 


17.9 


0.232 


0.541 


0.750 


0.922 


I 


09 


I 33 


1.51 


lO 


25 4 


0.328 


0.765 


1.06 


I 32 


i I 


•55 


1.88 


2.14 


20 


35 9 


0.463 


1.085 


15 


1.85 


2 


.19 


2.66 


1 301 


SO 


43 9 


0.567 


^33 


1.83 


2.26 


■ 2 


68 


3.26 


3-71 


40 


50.7 


0.656 


1-53 


2.12 


2.61 


3 


08 


3 76 


4.26 


50 


56.7 


0.732 


1. 71 


2 37 


2.82 


3 


47 


4.22 


4.77 


60 


62.1 


0.802 


1.88 


2-59 


3.20 


3 


79 


4.62 


5-22 


70 


67.1 


0.866 


2.02 


2.80 


3-45 


4- 


08 


4 97 


5 65 


80 


71.8 


0.925 


2.16 


30 


3 69 


4- 


37 


5 32 


6.03 


90 


76.1 


0.932 


2.29 


3.18 


3 91 


4 


64 


5 64 


6.41 


100 


80.3 


1.037 


2.42 


3-35 


4.13 


4- 


78 


5 93 


6.72 



Experiments referred to in an article by Professor J. R. 
Allen, of the University of Michigan, in Domestic Engineering, 
December 22, 1906, indicate that the actual velocity in hot- 
water circulating pipes is about 25 to 50 per cent of the the- 



128 



HEATING AND VENTILATING. 



oretical as given in the above table. The method usually 
employed in computing this velocity has been to consider the 
denser and lighter fluids occupying the relative positions shown 
in Fig. 43, the lighter fluid being in one branch of the U-tube, 
the heavier in the other.* If the cock be opened, equilibriiun 
will be established, and the lighter liquid will stand in the 
branch higher than the heavier a distance sufficient to balance 
the difference in weight. If we suppose (i) the cock closed 
and enough of the heavier material added to the shorter column, 

so that the heights in each are the same; 
(2) the cock opened, then the heavier Uquid 
will move downward and drive the lighter 
liquid upward with a velocity said to be 
equal to that which a body would acquire 
in falling through the distance equal to 
the difference in heights when the col- 
lunns were in equilibrium. This gives 
too great results, because it neglects the 
effect of the mass of the bodies moved. 
If friction be considered, we should have 
as a probable expression of velocity, 
using the same notation. 




Fig. 43. 



V-SOyj 



{Wi + W) I ' 



64. Flow of Water Through Pipes. — ^As water is heated 
it expands and its density grows less. At 70 degrees F., a 
cubic foot of water weighs 62.3 lbs. while at 200 degrees F. a 
cubic foot weighs 60.12 lbs. On the other hand, heated water 
flows with less friction. The pipe friction formulas are based 
on experiments with water at ordinary room temperatures, 
and if the results are figured in pounds of water without any 
allowance for temperature, the results can be applied to hot 
water without sensible error since the effects of the decreased 



• See Hood's work on "Warming Buildings," page 27. So far as the writer 
knows, this theory has not before been questioned. 



1U.0 

7.0 
tt.0 

-i-O 

4.0 



). 



1.5 



>> 



- 



:.:.:-:l 



^ ■ ■ • I* 



i .. . ■■:■■ » ■ 
• ■ I ■ 



■ « • ' 



: :.l: 



1 
:t: 



• - • ■ 

• • ♦ - 



■ » • • 



I 



rrr-rrr 



:j. I. Ti. ._»^ 7. V 'J 111 i/r_ 

. .' ./ ..»...— -I . . . , 

■■ - • - •■ v^- "y ■ ■* / ■ ■ r - -— — f 

: ■ .:/: ; /■ /; .. f - : r - : : 

« ... — .i/i*- — . ... •-** » •» y~ ■■^■i*' ■ ■ ■ ■ / ■ ■ ■ . ■« 

.• T ■ ■ ^,- ■/../»-- </ - • ■ - 



•..2_:V;.: _.., 

• ■ • • f / - ■ ' 



■f ' ■ / -■ ■/ / - ■ • ■ 



/ : 



■ ■ • i ■ 

... 1 

> ■ ■ • # ■ 

J_:_J 



I— ■ ;r :y-r , . "t/ - 

II , ■ f . ... 

..ill f 

/ ^ . L .1l._ * .'l. _';_. .'. 



■ / 






* — —^ 



• ■ ■ f : / 

■ I 



■■■/—:- 



.< / . '■ 






_i- . . .... / 

§ 



r : ■ t .- rr- 

f ■ ■ ■■ 

■ / ■ ■ ■ ■ 



f ■ 



I 

/ : 



2.0 - 



1.5 



■ 



1.0 - 

0.9 r- 

n.T :- 

n .r. • - 



1 . . . 

■ 



•».-> 



0.1 . 



I'.-.! 



L'.- 



I , 



0.;:.. 



"•' r: 



I.' 



M ^ 



Vi . : ' : • ■ -I k 



I- ■. . •; 



. . . : . t 



FLOW OF WATEE, STEAM AND AIR. 129 

friction and the decreased density of the water will then prac- 
tically cancel. In other words, the weight of water flowing 
will remain practically the same regardless of the temperature 
but the voliune will be affected by temperature changes. 

The generally accepted formulas for the flow of water through pipes 
are as follows when r= velocity in feet per second, J = diameter and / 
= length and A = head, all in feet: 



(Eytel wein) v = SOyjj—^ ; 

when d is very small with reference to / this becomes 



Idii 



(Hawksley) ^^Wz+sl^' 

when d is small with reference to / this becomes 




d becomes less than i per cent when / is lo feet for i-inch pipe and 50 
feet for a 6-inch pij)e. 

Other formulas as the Chezy where 

have a coefficient of friction which varies with the size of the pipe and 
with the velocity. 

Williams and Hazen's Hydraulic Tables have complete sets of pipe 
friction values for all ordinary conditions. 

Resistance of Pipe Fittings: Tests by F. E. Giesecke f with 
new 90-degree elbows give resistances of from 25 diameters for 

*The preceding chart was drawn from Schoder & Gehring values for pipe 
friction on page 320 of Hughes and Safford's "Hydraulics." 
t Professor of Architecture, University of Texas. 



130 HEATING AND VENTILATING. 

ij-inch pipe to 52 diameters with 7-inch pipe. Other fittings 
had the following equivalent values: 

I — 45-degree elbow equals J — 90 degree elbow. 

I — open return bend equals i — 90 degree elbow. 

I — gate-valve equals J — 90 degree elbow. 

I — globe-valve equals 12 — 90 degree elbows. 

I — tee equals 2 — 90 degree elbows. 

I — sleeve (negligible) equals -A — 90 degree elbow. 

I — radiator with valve and union elbow equals 7 — 90 degree elbows. 

65. The Flow of Air and Gases. — The flow of air obeys 
the same general laws as those which apply to liqtiids. The 
gases are, however, compressible, and the volimie is affected 
ver>* much by change of temperature, so that the actual results 
differ considerably from those obtained for liquids. These 
laws can only be expressed in mathematical formulas, from 
which, however, practical tables are derived. 

The flow of air from an orifice takes place under the same 
general conditions as those of liquids, and we have the general 
formula v = \^2gh as applicable. In this case // is the head 
which is equal to the height of a column of air of sufficient 
weight to produce the pressure. Air under a barometric 
pressure of 30 inches and at 50 degrees in temperature is 801 
times lighter than water. The pressure of air is usually meas- 
lured by its capacity of balancing a column of water in a U- 
shaped tube, which may be expressed in inches of water. One 
inch of water-pressure is equivalent to 67.9 feet of air at 60°, 
and increases ^\^ part for each degree of increase in tem- 
perature. The above formula is [only approximate, and does 
not account for the [change in temperatures and of pressures 
due to expansion, nor for friction head, contraction of dis- 
charge, etc.; its results are always liigh. Professor Unwin 
gives in the article " Hydromechanics," Encyc. [Brit., the 
following formula for computing the velocity of flow of air 
from an orifice: 






^^lAi 



FLOW OF WATER, STEAM AND AIR. 131 

r= absolute temperature; 

^1 = absolute pressure in vessel from which flow takes place; 

^s= absolute pressure in surrounding space. 

< 
To find the volume discharged the velocity must be multiplied by 

the area, and that result by a coeflScient which Prof. Unwin gives as 

follows: 

Conoidal mouthpieces of the form of the contracted vein, c= 

with eflfective pressures of .23 to i.i atmosphere 097 to 0.99 • 

Circular sharp-edged orifices 0-563 * * 0.788 

Short cylindrical mouthpieces 0.81 ' ' 0.84 

The same, roimded at the inner end 0.92 * * 0.93 

Conical converging mouthpieces 0.90 * * 0.99 

Weisbach gives as a formula for efl3ux of air under small 
pressure 

in which 

F = area of discharge orifice; 

7 = the weight per unit of volume; 

^ = initial absolute pressure in vessel from which flow 

takes place; 
A = absolute pressure into which flow takes place; 
6 = the atmospheric pressure; 
M = the coefficient of discharge having the following values 

for pressure less than | that of the atmosphere: 
(i) for an orifice in a thin plate; m =0-56; 

(2) for a short cylindrical pipe; m=o.75; 

(3) for a well-rounded-oflF conical mouthpiece; /i=o.98; 

(4) for a conical pipe whose angle of convergence is 
about 6^; /x=o.62. 

If we denote by t the absolute temperature in degrees cen- 
tigrade, the last formula may be written, for dimensions in feet, 

Q = i2ggfjLF'J {1+0.0047)- cubic feet per second. 



134 HEATING AND VENTILATING. 

For a velocity of loo feet per second r varies from 0.00484 to 0.01212 
for a diameter varying from 1.64 ft. to 0.164 ^t. 

For a temperature of 60^ F. and for a pipe one foot in diameter and 
100 feet long ^•= 0.006. For barometer reading of 30 inches, pressure 
being expressed in inches of water, #0=407, we have 

«o= I.512 V(/>o-pi)(/>o-f />i). 

From the above formula the third column in Table XXVI of Appendix 
is computed. It is noted from the general formula for velocity, that 
the velocity varies as the square root of the diameter in feet divided by the 
length; from this it follows that to obtain the velocity for lengths and 
diameters other than given, the results in column (3) must be multiplied 
by 10 V(///. 

The fourth colunm of Table XXVI gives 0.7 of the theoretical velocity 

t= 'w 2gh under the conditions named above. It is to be noted that for 
velocities less than 40 feet per second the results by the latter method 
of calculation would not be greatly in error. 

M. Ledoux states that the formula giving the pressure p at the extrem- 
ity of a straight horizontal conduit which is supplied with a volume Q^ 
cubic meters of air per second at the pressure #0 and the temperature To 
is as follows: 

#'=#oM 1—0.0001012—^—^ )in metric units, centigrade degrees. 
\ io-a* / 

From this the diameter of the pipe in meters is 




^Tl 
J= 0.1589 / 7-^ — ITV^" metric units, centigrade degrees. 



Diameter in feet equals for a given flow of Q cubic feet per minute, 
English measures (feet) and Fahr. degrees, 



a =0.0217 ' 



H) 



To^ 



This formula agrees closely with that of Prof. Unwin, given above. 



FLOW OF WATER, STEAM AND AIR. 135 

66. Experiments on the Flow of Steam Through Pipes. — * 

Where steam flows in a given pipe there are several factors which 
tend to dissipate or change the form of energy possessed by the 
steam. These may be classified as follows: (a) condensation, 
(6) friction, (c) expansion with changes of external energy, (d) 
the effect of gravity. 

(a) The condensation may be divided into two parts, one 
the static condensation, that which occurs when there is no 
flow of steam; the other the dynamic condensation which occurs 
when there is a flow of steam. The latter should be less than 
the former on account of fall of pressure and temperature at the 
delivery part of the pipe, which tends to raise the quality of the 
steam, but the fall in pressure also involves a change in kinetic 
energy, and this, with other influences, seems to have made 
the amount of condensation very nearly the same for both cases. 

(6) The friction in the pipe would cause a loss of pressure 
and require work to be done. If the pipe were a non-conductor 
and the expansion adiabatic, then there would be no loss of 
energy, but there would be a transformation of initial potential 
energy into external and kinetic. This change of energy 
between two points could be equated to a form involving the 
coefficient of friction, and its value thus derived. In practical 
work the adiabatic condition is seldom or never realized, for a 
pipe may be covered ever so well and still there is a loss of 
heat. 

(c) The expansion would cause change in external latent 
energy which is accounted for by the steam table under different 
absolute pressures. 

(d) The effect of gravity may be considered as nil in this 
series of experiments, as the pipe was horizontal. If the pipe 
were inclined any perceptible amount from the horizontal, the 
work could be computed, due to the delivery, and the height 
through which the steam raised or fell. We shall consider 
only the case of a straight, horizontal pipe. 

* By E. C. Sickles and the Author. Presented at the New York meeting 
(1898) of the American Society of Mechanical Engineers, and forming part of 
Volume XX. of the Transactions. 



HEATING AND VENTILATXNU. 



TABLE 1.— FLOW Of 



n Presjure on RiEbl, (■ 



Dianietec 


.4" 1 «■ .0- a- 


.6- 


»■■ 


■ 4" 


.3'' 


1," 


„ 


1." 


DlKhsrtfe 


11™ 


11.188 SjVi, 667» 
I0.3siai44, 6lOi 




JS60 


34»' 


Si 




18S3 

!slo 


:t:t 










































































6gos 




3wi 














87* 




























7,S00 




Jtlf ^^^^ 




"T 




.53* 


"#» 












J^S^ 








ut: 




',U1 


ifj, 














































































:g?s 


;*S' 




i?3 


H? 


at 


SiO 

4*3 


464 
30f 




t'.^ot 


'■^li "ui 


?fi 


Hi 






i? 


■1; 


30 s 
IBS 


s 




'- 


*"i ^'^ 


us 


U6 


lis 


"* 


103 


BJ.. 


'^6.0 


si. a 


Diuncler c" 


8" 


7' 


6" 




4- 


Ji" 


3" 


Jt" 


=■■ 


.rl .- 


DlKh>rt(e 


'i; 
iti 


i 

4lB 
4O0 


J6l 




i 




6»!6 
6S.6 

'""ft 


m's 


1 




































































































"* 


1™ 


I JO ' J'l't 




i6? 


Jtti 


Mi 




tM 


























;■» 


























"i 


gJ.T 




'M 


'^J 










Si! 


°" 




ae.o 


''" 


" 1 "' 




4.4 


1,98 


>.oo 


■•" 


0.64S 


O.09 



FLOW OF WATER, STEAM AND AIR. 



137 



STEAM IN PIPES. 



E. C. Sickles, M.E. 



Length of Pipe, One Thousand Feet. 



Drop in Pressure in Pounds per Square Inch. 

Corresponding to Discharge on Left; Densities and Corresponding Absolute Presssures 

per Square Inch in First Two Lines. 



Density . 


.208 


1.215 


.222 


.230 


Pressure 


90 


93 


96 


100 


Drop . . . 


18.10 


17.5 


16.9 


16.4 




15.60 


15. 1 


14.6 


14. 1 




13.3 


12.8 


12.4 


12.0 




II. I 


10.7 


10.4 

8.66 


10. 




9.2s 


8.94 


8.36 




8.33 


8.05 


7.80 


7.53 




7.48 
6.67 


7.23 


7.01 


6.76 




6.45 


6.25 


6.03 




S.91 


5.71 


5.54 
4.86 


5.35 




5.19 


5.02 


4.69 




4.5a 


4.37 


4.24 


4.09 




•3.90 


3.77 


3.6s 


3.53 


• * • . . 


3-32 


3.21 


3. II 


3.00 




a. 79 


2.69 


2.61 


2.52 




2.31 


2.23 


2. 16 


2.09 




Z.87 


1. 81 


1.75 


1.69 




1.47 


1.42 


1.38 


1.33 




1. 13 


1.09 


1.06 


1.02 




.831 


.804 


.779 


.752 




.577 


.558 


.541 


.489 




.369 


.356 


.346 


.334 




.208 


.201 


.195 


.188 




.0923 


.089 


.086 


.0835 




.0231 


.0223 


.0216 


.0209 



.239 
104 

158 
13.6 
II. 6 
9.66 
8.05 
7.25 
6. SI 
5.80 

5.14 
4.52 

3.93 



.248 
108 

15.2 114.7 
13.0 :i2.7 
II. 2 10.8 



.306 .316 

I3S I 140 



Density . 
Pressure 



Drop 



« . 

• « 
( « 

It 

* * 

* * 

* • 

* I 

* • 
« • 

* * 

« • 

a • 
• < 
< ( 



327 

145 



II. 5 
9.92 
8.46 
7.06 
5.88 
5.30 
4.76 
4.24 
3.70 
3.30 
2.87 
2.48 
2. II 
1.77 
1.47 
I. 19 
.935 
.719 
.528 

;.367 
'.235 

1.132 
1.0587 
I. 0147 



338 
150 



II 

9 
8 
6 
5 

5 
4 



I 

60 
18 
83 
69 
13 
60 
4.10 
3.64 
3.19 
2.78 
2.40 
2.04 
1.72 
1.42 
1 . 15 
.905 
.695 
.511 
.355 
.227 
.128 
.0568 
.0142 




138 HEATING AND VENTILATING. 

General Equations. 

If P be any pipe of uniform diameter, d, and Ei the energy of 
the steam entering a section, as ^4, in one second, and £2 the 
energy leaving a section JB, at the distance of L feet from A, 
then 

Ei-E2=Ec+Er+Ee+E, (i) 

where £c = dynamic condensation energj-; 
£/= friction energ)-; 
Eg = expansion energy ; 
£f= gravitation energy. 

Now, since in steam tables the energj' £, of the latent external 
energ}' is included in the total energy of steam at any pressure, 
it need not be considered for our present purpose; also E, is 
negligible because our pipe is horizontal. 

Writing £/ and £2' for the new form of (i), we have: 

£/-£2'=£c+£/ . (2) 

This is an indeterminate equation for certain values of Et and 
Ef, but if Ee can be determined by direct measurement, or if the 
pipe can be so protected that the condensation loss is negligible, 
the equation becomes determinate. It is also possible to make 
the velocity of steam so much that the heat developed by fric- 
tion shall make the loss bv condensation zero, in which case 
the equation b also determinate. Let the total loss of energ}' 
be denoted bv £, then we have that 

E=Ei'-E2=E,+Ej (3) 

from which 

£-£c = £/ U» 

\'ariou5 expressions for the value of £.. the loss by friction, 
have biXMi civen bv various writers, and an excellenl discussion 
of the results obtaini\: by i:f<^ 01 diiTcrcnt fom^ulx is given in 
£iii:/M<rr;wc. March 10. 1S07. by Mr. Arthur J. Martin. 



FLOW OF WATER, STEAM AND AIR. 139 

It seemed desirable, after obtaining unsatisfactory results 
with other formulae, to reduce all experimental results by the 
formula given by Unwin in article " Hydro-Mechanics," page 
484 {Encyclopaedia Brilannica), which is reduced from Weisbach. 
In accordance with this formula the frictional work is for the 
length of pipe L, 

^'^fva^^^^n 1^^ (5) 

2g d g d 

In which /=coefl5cient of friction, F = velocity in feet per 
second, (/ = diameter in feet, Pr = weight of fluid per second. 
This substituted for Ef in equation (4) gives 

1/2 2 

£-£c=/— jPTL (6) 

g d 

The value of Ec was found by experiment to average 1,700 foot- 
pounds per second for the pipe, protected as well as possible 
by covering. 

The loss of head 

g d 

m 

Let p equal loss of pressure in pounds per square inch, and 
D density of the fluid or weight per cubic foot, then will 

P = • 

144 

The values of the coefficient obtained in these experiments do 
not differ materially from those obtained by the experiments 
cited in vol. xii., Encyclopcedia Britannica, article " Hydro- 
Mechanics.*^' Professor Unwin gives formulae for the coefficient 
of friction for flow of water through pipes, as follows: /= 0.005 
(i-fj^j), and for a slightly incrusted pipe, /=o.oi (i+ils). 
For the flow of air, by experiments at St. Gothard timnel: 



/=o.oo28f i+-^)for air. 



140 HfATDfG AXD VENTILATING. 

By experiments by M. Arson on pq)es which were probably 
router. 



/=o^s(i+^)£orair. 



The experiments at Sibley College, which have been died, 
indicate a value of the coeflident of friction for steam Rowing in 
pipes, as follows: 



/=o.oo223j iH — ^)for steam. 



The experiments at Oriskany indicated the coeffident of fric- 
tion: 

/=o.oo26( iH — Tj)^^^ steam. 
The tables were calculated for a coeffident of fricticMi, 



/ =0.0027/ 1 H — ^) for steam. 



In the last five formulae, d, the diameter, is to be taken 
in feet. 

The complete expression for loss of head in pounds, p, is 
obtained by substituting the value 0.0127 'or K in equation (11), 
in which case 



p= 0.00013 1 



\ ^ d' JDd'^' 



in which d'= diameter in inches, £= length in feet, Z?= density. 
The discharge in pounds per minute 



»-87.4S ■ '"• 



The diameter in inches 



^-'■"•^^li'^i) 



These formulae also agree dosely with experiments made by 
Ledoux. 





IILS 


Absolute Btoara Pitman 

M (l! I l,S « 


nt HlOdle <a LioB. iDohe. of Sm-cary 

1 i * a !» IS 




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111 




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x-k- 




tajm 




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s\ 


\ ^ 






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\ 


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x\ 




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s\ 


\\ 


m^ 


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\ 


\ 


\ 


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\ 


\ 


\ 


v 
N 




\\ 


\^ 


»fa» 




\ 


\ 


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\ 


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k\ 


s 


s 


\ 


\ ^ 








\ 


\ 


\ 


\ 


\ 


\ 


n\ 




s^ 


\\ 


\ \ 


IMM 






\ 


^ 


\ 


\ 


^ 


\ 


\ 


\' 




^ 4 




•MM 
IMM 






\ 


\ 


\ 


S^ 


k ^ 


\ 


\ 


\ 


\ -- 


!i )l. 


UMt 




\ 




\ 


\ 


\ 


S^ 




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\ 


\ 


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IWN 








Si- 


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:v 


A 


Au 




Li. 


?_^ 


il^-^J. 


-i.J- 





IiOaBotPrcnuroperKnFt.ur Pipe, PounilB per ■q.Iiioh 



FLOW OF WATER, STEAM AND AIR. 141 

Friction of Pipe, Fittings. — For steam, the length of pipe 
in inches equivalent to one elbow is 

and to one globe- valve 

where d' and L' are both in inches. 

The loss through gate-valves was found to be negligible. 

67. Charts for Flow of Steam in Pipes. — The following 
charts, taken from Power and prepared by Prof. H. V. Carpenter, 
of Washington University, present a ready means of obtaining 
the velocity of steam in feet per minute and also the steam 
delivered in pounds per minute. The charts were developed from 
experiments made by Mr. Sickles and the author and are ex- 
tended over a somewhat wider field, but the results seem to 
check quite well with practice so they can perhaps be accepted 
as representing the truth as closely as is possible at present. 

The method of reading the charts is shown by the heavy 
dotted lines; for example, following the dotted lines on the 
velocity chart, it is found that if the loss of pressure is assumed 
to be I lb. per 100 feet of pipe, in a 12-inch pipe, and the 
absolute pressure is 5 lb. per sq.in. at the middle of the pipe 
line, then the velocity of the steam will be a little over 41,000 
feet per minute; or, if the pressure is 3 inches of mercury the 
velocity will be nearly 74,000 feet per minute. 

In a similar way the quantity chart shows that, with a 
drop of I lb. per 100 feet, in a 12-inch pipe, and an average 
pressure of 5 lb. per sq.in., the quantity of steam delivered 
will be 440 lb. per minute; or if the pressure is 3 inches of 
mercury, 250 lb. per minute will be delivered; or if the pres- 
siu^e is I inch of mercury, 150 lb. will be delivered. 

The charts may, of course, be worked in any direction 
so that if any three of the quantities are known or assumed 
the fourth may be determined. 

It will be noted that by using both charts for the same 



142 HEATING AND VENTILATING. 

case the velocity required to deliver a given quantity of steam 
per minute may be determined; for example, in the first case 
given above it follows from the results obtained with both 
charts that to deliver 440 lb. of steam per minute through a 
12-inch pipe at an average pressure of 5 lbs. absolute, a velocity 
of 41,000 ft. per minute will be required. 

All of the charts are calculated for saturated steam. There 
should be little error, however, in their use for superheated 
steam provided that instead of the actual pressure of the super- 
heated steam we use the pressure at which saturated steam 
has the same weight per cubic foot. 

In the calculation of the charts it has been assimtied that 
the nominal diameter of the pipe is its actual diameter. The 
error due to this will not be noticeable, except, perhaps, for 
piping over 12 inches in diameter, which is rated by its out- 
side diameter. In these larger sizes the actual inside diameter 
should be used in applying the charts. 

If it should be desired to apply the charts to pipes which 
are not circular in cross-section, it would be necessary to 
calculate the hydraulic radius (cross-section divided by perim- 
eter) of the conductor. This multiplied by four would be the 
equivalent diameter. 

The enormous velocities which the velocity chart shows 
to be permissible at low pressures emphasize the need of avoid- 
ing sudden bends or offsets in condenser piping. 

68. Dimensions of Registers and Flues.- -The approxi- 
mate dimensions of registers and flues can be computed from 
consideration of the limiting velocity of entering air. 

For residence heating the velocity in flues is likely to be as 
follows, in feet per second : 



Warm-air Ventilating 

Dutt. Duct. 



Fin«t stor>- ^ . 5 to 4 6 

Second stor>- 5 5 

Third stor>' ' 4 

Altic floor 7 3 



Entering Air 
at Register. 



3 
3 
3 



Discharge Air 
at Register. 



4 
4 
3 
2i 





Abeolute Steam Prewura nt 

U II B 


<Hd 


He at 


Lino. 


iDohM of 


He 




?; 




- 


Pnpnilspe 


— " 


> 




















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^ 






^ 


k 




~ 


^, 








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- 


^^ 








^ 




- 


- 






^, 




^ 


^ 


^ 


■^ 


- 


^ 




■--^ 


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^ 




^ 


^ 




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^ 


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^ 


^ 


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- 


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^ 


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Low <>t PrCMuro iwr HP Ft. i>r Pl|ic, rounib" inT^'i. Iiic 



FLOW OF WATER, STEAM AND AIR. 



143 



The velocity per hour being 36CX) times that per second, the 
area of the duct can be found by dividing the cubic feet of air 
needed per hour by 3600 times that in the above columns. If 
the air required is taken as a certain number of times the 
cubic contents of the room the following method is applicable: 

If we denote the cubic contents of a room by C, the num- 
ber of times the air is to be changed per hour by », the velocity 
in feet per second by V, then will the area in square feet 



A = 



nC 



In square inches a = 



nC 



36007 '' 25 F' 

The following table gives the net area in square inches for 
each 1000 cubic feet of space, of either the hot-air or ventilat- 
ing register, for any required velocity of the air. The net 
area is about 0.7 the nominal area. (See Table of Registers, 
in Chapter XIII.) 



AREA IN SQUARE INCHES FOR EACH 1000 CUBIC FEET 

OF SPACE 



Velocity. Feet 


Number of Times Air Changed per Hour. 


per Second. 


I 


2 


3 


4 


5 


6 


8 


10 


I 


40 
20 

^3 3 
10 

8 

6.7 

5 

4 

2.7 

2 

1.6 

1-3 


80 
40 
26 
20 
16 

13 
II 

8 

5-3 
4 

3-4 
2.7 


120 

60 

40 

30 

24 
20 

IS 
12 

8 

6 

4.8 

4 


160 
80 

53 
40 

34 
27 

20 

17 

II 3 

8.5 
6.8 

5-7 


200 
100 

67 
50 
40 

33 

25 
20 

13 3 
10 

8 
6.7 


240 
120 

80 

60 

48 

40 

30 

24 
16 

12 

9.6 

8 


320 
160 
107 

80 

64 

53 
40 

32 
21 
16 
12.8 

10. 5 


400 
200 


2 


Z 


133 
100 


• 

A 


C 


80 


' ' ' * 

6 


67 
50 
40 
26.6 


8 


10 


ic 


J 

20 


20 


25 


16 


J************ 
^0 


13.3 


** 



In some instances the amount of air can be computed as 
a function of the cubic contents of the room, especially when 
required for ventilation alone. For ventilation purposes the 
problem of proportioning the air-passages is solved simply by 
computing, first, the air required, on the basis of 1800 cubic feet 
per hour for each person who will occupy the room; second, 



144 HEATING AND VENTILATING. 

the number of times the air will be changed per hour^ by 
dividing this result by the volume of the room. 

In applying this method to practical problems, it is best to 
proportion the ducts so that in no case will the required velocity 
of the air in the flue exceed 12 feet per second or 43,200 feet 
per hour, an amount not likely to be reached without a fan 
or blower, and one which corresponds to a pressure of nearly 
o.i inch of water. 

69. Dimensions of Registers. — The registers should be 
so proportioned that the velocity of the entering air will not 
be sufficient to produce a sensible draft; that is, the area must 
be such that the velocity shall not exceed 3 to 5 feet per 
second or 10,800 to 18,000 lineal feet per hour. The writer 
thinks that very excellent results are obtained by proportion- 
ing the registers for first floor so as to give velocity of 2J 
feet per second, and those of higher floors and at entrance to 
ventilating-shafts 3 feet per second. The results above, except 
for entrances to ventilating-shafts on the top floor, are less 
than is usually produced by natural draft, so that the area 
computed by dividing the total amount of air required by the 
number which expresses the velocity gives satisfactory results. 

The above rules are for effective or clear opening, and this 
will be found in each case to be about two-thirds of the nomi- 
nal or rated size of the register as shown in the table given in 
Chapter XIII. 

By computing, from the data given, the number of changes 
of air per hour in room, the table on the preceding page can 
be used as explained to determine the effective area in square 
inches required for each 1000 cubic feet of space. 

70. Size of Ducts for Indirect Heating. — An approximate 
method of computing the sizes of air-flues would evidently 
be that of dividing the total amount of air which is required 
in a given time by that delivered or discharged through a flue 
one square foot in area. A table is given for capacity of 
ventilating-pipes, see Appendix, Table XXV. 

As an illustration, consider that of a room with 48 square 
feet of glass surface and 320 square feet of exposed wall surface. 



FLOW OF WATER, STEAM AND AIR. 



145 



and from which the heat loss per degree difference of temper- 
ature is 128. Supposing air in room to be 70° F. and that 
supplied by flue to be 100° F., we see by table page 265 that for 
every heat-unit as above there will be required 135 cubic feet 
of air per hour, and for this case we will require 135X1 28 =517,280 
cubic feet per hour. If excess of temperature of aii in flue 
over that outside be considered as 50°, and height of flue as 10 
feet, the discharge per square foot of flue (see table in Appendix) 
will be 242 feet per minute or 14,520 per hour. Hence the 
required area of the flue will be 17,280 divided by 14,520=1.19 
square feet = 17 1 square inches. Areas of flues may be computed 
by the following table, making suitable allowance for friction. 









(E<« 


■ «., 


Bperat« 


„[,i. 


;al1o. 


..»r. 




n, 0.) 






J 


4 






Hciglit or Kcsd 


DlPlu 


inP« 




























11 


s 


,. 


.= 


" [ JO 


.. 


„ 


.0 


so 


... 


li 




























Ar» ot Flu. 


.Sq.u 












« 




















fl.T.U. 
71M 


B.T.U. 






, 


!.. 


V^ 


!■; 


i.s 


J.. 


I, 


!■! 


\ 


80a 


4° 


t 




as 




\t. 


lJ:i 


:t 


W, 




;;■! 


,! 


000 


MS 


00 

ii: 


iH 


S8 


1 


;! 


'i 


i 


48 


38 
46 




n 


s: 


a SO 


J40 

JOO 


iiS 


is; 


'S, 


•,\i 


101 


i; 




It 


ii 


i 


z 


5lo 


s 


r:. 


i; 




1S4 

ii 


163 


\l\ 




\i 


IS 








;goo 




1060 










45S 
























































n«,ooo 


30OQ 


'" 


■"■*" 


"" 


'""'" 






loss 






S.7 



T»ble U eomputed by finding__Bir reouirrd to lupply hca 

Maare'ool io'area for^tht given htight and > diSrence at temo 
Id Table XVI. Aclusi fluci should be takea i 



without Bill 



n th<i table. It ihould be noted that tbii table givei the aiEi 
Tance for lou due to fiiclion. and in practice the leiulti mult be ii 

jDatef/ equal to area of gUu plua one-foufth the eipOHd wall-iurface 



146 



HEATING AND VENTILATING. 



As the velocity of flow increases with difference of tem- 
perature between outside air and that in the flue, and is 
lessened when this difference is small, it is better to assume 
a mean difference of temperature so low that the computation 
will certainly afford plenty of air for ventilation. 

The preceding table is computed by the method explained 
for different heights of flue and for a difference of temperature 
of the air in the flue over that in the space into which it dis- 
charges of 30® F. 

For difference of temperature other than 30° multiply 
results in the table by the following factors to obtain the area 
of the flue : 



Difference 
Temperature. 
Degrees. 


Factor. 

1 


Difference 

Temperature, 

Degrees. 


Factor. 


10 
20 
40 


1-74 
1.22 

0.87 


50 
60 

70 


0.77S 
0.71 

0-655 



For usual conditions of residence heating in which the air 
in the supply-flue is 30° above the temperature of the air in 
the room, and that in the ventilating-flue 20°, we may compute 
the approximate area in square inches of the supply- and venti- 
lating-duct, by multiplying each heat-imit per degree difference 
of temperature lost from the walls by a series of simple factors 
which are easily memorized. 

TABLE OF FACTORS FOR AREA OF AIR-FLUES. 





Supply-duc». 


Ventilating-duct. 


Story of Building. 


Approxi- 
mate 

Head in 
Feet. 


Velocity 
in Feet 
per Sec. 


Factor for 

Area, 

Sq. In. 


^PP?*'- i Velocity 

Distance »2r &^^ 
to Roof. P*' ^***^- 


Factor for 

Area. 

Sq. In. 


First Floor 

Second Floor 

Third Floor 

Fourth Floor 


(l) 

5 
28 
40 
50 


(2) 
2.8 

6.8 
8.1 
9.0 


(3) 

2.40 

0.9s 
0.82 

0.71 


(4) 
47 
32 
20 
10 


(5) 
5-5 
42 
36 
2.6 


(6) 

93 
1.27 

^'33 
2.17 



FLOW OF WATER, STEAM AND AIR. 147 

As an example, find the required area of heat- and venti- 
lating-ducts for a room with 200 square feet of exposed wall- 
surface and 30 square feet of glass; 30 plus one-fourth of 200 
is 80, the approximate building loss per degree. This quantity 
multiplied by factors in columns (3) and (6) gives respective 
areas of flues in square inches with suflScient exactness for 
ordinary requirements, 

71. Roof Ventilators. — There are a number of roof ventilators 
of different designs on the market. Some have wire glass tops 
so as to light the vent flue, and are equipped with automatic 
dampers controlled by a fusible link which closes it in case of 
fire. They are made in two general types, one with a rotating 
cowl with the opening on the leeward side, the other with a 
stationary top and hood. A roof ventilator tested by the 
author, showed good ventilating action when placed in a 
horizontal air current. 

72. Power for Moving Air Through Ventilating System. — 
Air is moved through a building and its ventilating system 
only by some form of power expenditure. When uncon- 
fined air is warmed, approximately one-third of the heat 
imparted to it has no effect in raising its temperature, and is 
expended in the work of expanding the air. That work put 
into and stored in the air is, in part at least available for 
ventilating purposes. It is that which makes ventilation by 
gravity methods possible, and, imder conditions designed with 
reference to that end, wholly inexpensive so far as the mechanical 
side of the problem is concerned. The working pressiure 
which is due to differences in temperature and in weight between 
the air inside and the air outside of a building varies through 
a wide range. Even where that pressure is greatest it is yet 
so small that a close and dust-fiUed cobweb can resist it and 
arrest air-flow. 



CHAPTER VI. 

PIPE AND FITTINGS USED IN STEAM AND HOT-WATER 

HEATING. 

56. General Remarks. — In this chapter will be found a 
condse description of pipe and fittings to be had regularly of 
most dealers. Such a description is entirely unnecessary to 
those familiar with current practice in the industry of steam 
and hot-water heating; but as the writer has foimd by experi- 
ence detailed knowledge on this subject is often required, the 
following descriptions are deemed necessary. 

It may be remarked in a general way, that for conveying 
heated air, galvanized or tin pipe or brick flues are usually 
provided, but for the purposes of conveying steam or hot water 
wrought-iron pipe is used almost exclusively. 

57. Cast-iron Pipes and Fittings. — Cast-iron pipe was used 
very largely at one time for both supply-pipe and radiating 
surface in hot-water heating, but at present it is used only to 
a limited extent in greenhouse heating. For this purpose 
one size of pipe only is used, and this is j^" outside diameter. 
The pipe weighs about 12 lbs. to the foot, and has a capacity 
of i gal. per foot. The pipes are usually joined by socket- 
joints, for which purpose a socket is cast on one end of each 
pipe. The joints are formed by inserting one end of one pipe 
into the socket of another and filling the interspace either 
with melted lead, iron filings and sal-ammoniac, sulphur, 
iron cement, or red lead. The lead joint, which is ordinarily 
used, is formed by making a mould, by wrapping a hemp rope 
covered with day around the joint, with a pouring-place on 
top into which the melted lead is nm. After the joint cools 
the lead is driven into place with a calking-iron. The rust- 

148 



PIPE AND FITTINGS. 



fjoint is a very excellent joint, and often used. It is made with 
I -a cement formed by saturating for ten or twelve hours iron 



(<,r Ciist- 
1 Pipe. 



Fig. 44.— Cast-iroQ Pipe with Socket. 

turmngs or filings with sal-ammoniac. This cement is pressed 
into the socket, and then pounded tightly into place with a 
calking-iron. Joints made with Portland cement 
are sometimes used, but they are, likely to 
crack from the heat, and, cannot^ be recom- 
mended. 

The regular form of pipe and some of the 
principal fittings are shown in Figs. 44 to 48. 

Special brackets are usually used where two 
or more lengths of pipe arc run in parallel 
lines with a sUght descent in the direction of 
the flow, and thus serve both for radiating sur- 
face and circulating pipes For greenhouse 
heating, where the air is to be kept moist, 
a special pan to be filled with water, as shown 
in Fig. 47, supported by the pipes, is used at 
inter\'als. 

For the purpose of checking or stopping 
the flow a stop consisting of a flat plate, which 
can be set at any angle with the pipe, and of a form as in Fig. 
48, is used. Each length of cast-iron pipe is sometimes prc>- 



FlG. 46.— 
Round Tee for 
Casi-iron Pipes. 




Fio. 47. — Radi; 



and Pan for Holdirg W.iter to Moisten Air. 



vided with flanges, and joints are made by bolting the pipes 
together, packing being inserted to prevent leaks. These are 
inferior to the calked joints. 



i 



ISO 



HEATING AND VENTILATING. 



58. Wrought-iron and Steel Pipe, — Pipe made of wrought 
iron or milri steel is generally used for the purpose of convey- 
ing steam or hot water in heating systems. This pipe is made 
in a number of factories and of standard sizes, so that the 
pipe obtained from one is reasonably certain to fit that from 
another. Wrought-iron or steel pipe is made from metal 
of the proper thickness, which is rolled into pipe shape, and 
raised to a welding heat, after which the edges are welded 
by drawing through a die. The smaller sizes, ij inch and 
under, are butt-welded; the larger sizes are in all cases lap- 
welded. 

Lap-weld Process.— Va.t following description is taka 

from the National Tube Com- 

pany's Handbook for 1913. — 
" The skelp used in making lap- 
welded tubes is rolled to the 
necessary width and gauge for 
the size tubes to be madcj the 
edges being scarfed and over- 
lapped when the skelp is bent 
into shape, thus gi\'ing a com- 
paratively large welding surface, 
compared with the thickness of 
the plate. As a result of the 
work done in forging down the 
metal at the weld, tubes made in this way will probably be 
stronger at the weld than at any other place. 

The skelp is first heated to redness in a " bending furnace." 
and then drawn from the front of the furnace through a c^e, 
the inside of which gradually assumes a circular shape, so that 
the skelp when drawn through is bent into the form of a tube 
with the edges overlapping. 

In the next operation the skelp so formed is heated evenly 

to the welding temperature in a regenerative furnace. When 

the proper temperature is obtained, the skelp is pushed through 

SD opening in the front of tliis furnace into the welding rolls. 

ing between two rolls set one above the other, each having 




Fic. 4B.— Valve or Stop for 
Cast-iron Pipe. 



PIPE AND FITTINGS. 151 

a semicircular groove, so that the two together form a circular 
pass. Between these rolls a mandrel is held in position inside 
the tube, the lapped edges of the skdp being firmly pressed 
together at a welding heat between the mandrel and the rolls. 
The tube then enters a similarly shaped pass to correct any 
irregularities and to give the outside diameter required. It 
will be noted that the outside diameter is fixed by these rolls; 
any variation in gauge, therefore, makes a proportional varia- 
tion in the internal diameter. This also applies to butt-weld 
pipe. Finally, the tube is passed to the straightening, or cross 
rolls, consisting of two rolls set with their axes askew. The 
surfaces of these rolls are so curved that the tube is in contact 
with each for nearly the whole length of the roll, and is passed 
forward and rapidly rotated when the rolls are revolved. The 
tube is made practically straight by the cross rolls, and is also 
given a clean finish with a thin, firmly adhering scale. 

After this last operation the tube is rolled up an inclined 
cooling table, so that the metal will cool off slowly and 
imiformly without internal strain. When cool enough the 
rough ends are removed by cold saws or in a cutting- 
off machine, after which the tube is ready for inspection and 
testing." 

This pipe is put on the market in three different grades of 
thickness: first the standard grade, which is used principally 
for heating purposes; this is tested to a pressure of 250 lbs. 
per sq. in. and has the dimensions given in Table XVIII; it 
is manufactured in sizes from | in. to 15 in. in diameter. 
Thicker pipe, called extra strong, and still heavier pipe called 
double-extra strong, is manufactured, and can be obtained if 
required. The thick piping has the same distinguishing name 
as pipe of standard weight, having the same external diameter, 
which is in all cases that of the external diameter of the stand- 
ard pipe. The extra-strong and double-extra strong have 
smaller internal diameters than would be implied by the name; 
thus, for instance, inch pipe, standard size, has an inside diam- 
eter of about one inch, an outside diameter of 1.315 inches, 
while the extra-strong pipe of the same nominal size has the 



152 HEATING AND VENTILATING. 

same outdde diameter and an inside diameter approziinately 
0.951 inch, while the double-extra strong has the same outside 
diameter and an inside diameter of 0.587 inch. 




Fig. 4Q. — Section of Standard Pi|)es 1 to j inches Nominal Size. 
The following table gives the diameters, external and in- 
ternal, and weights per foot, of the various kinds of pipe. In 
the table* the normal inside diameter is the actual diameter, 

■ See more enlended tabic in ApDcndii. 



PIPE AND FITTINGS. 



153 



or nearly so, for the standard pipe; sizes to li inch are butt- 
welded, larger sizes lap-welded: 



Nom- 
inal Di- 
ameter 
iname), 
nches. 



i 
i 
i 

i 

A 

4 

I 

li 

2 

3 

si 

4 

Ai 

5 
6 



Actual 
Out- 
side 

Diam- 
eter, 
Inches. 



0.405 

0.54 
0.675 

0.84 

0.105 

1-315 
1.66 



9 

375 
875 
5 



563 
625 



Actual Inside 
Diam., In. 



Extra 
Strong." 



0.215 
o 302 

423 
546 
742 

957 

278 

1.500 

t 939 

2.323 
2.900 



364 
,826 

290 

813 
761 



Double 
Extra 
Strong. 



0.252 

0.434 

0.599 
0.896 

1 .100 



1-503 
I. 771 
2.300 
2.728 

3-152 
3.580 
4.063 
4.897 



Thickness of Iron. 


Weight per Foot, 


Inches. 




Pounds. 


Stand- 
ard. 


Extra 
Strong. 


Double 

Extra 

Strong. 


Stand- 
ard. 


Extra 
Strong. 


Double 

Extra 

Strong. 


0.068 


0.095 


• ■ • • 


0.24 


0.31 


• • • • 


0.088 


O.I19 


• • • • 


0.42 


0.54 


• • • • 


0.091 


0.126 


a • • • 


0.56 


0.74 


• ■ • • 


0.109 


0.147 


0.294 


0.85 


1.09 


1. 71 


O.I13 


0.154 


0.308 


I -13 


1.47 


2.44 


0.133 


0.179 


0-358 


1.68 


2.17 


3.66 


0.140 


O.191 


0.382 


2.28 


3.00 


5 21 


0.145 


0.200 


0.400 


2.73 


3-63 


6.40 


0.154 


0.218 


0.436 


3 67 


5 02 


9 03 


0.203 


0.276 


0.552 


5-81 


7.66 


13.69 


0.216 


0.300 


0.600 


7.61 


10.25 


18.58 


0.226 


0.318 


0.636 


9.20 


12.50 


22.85 


0.237 


0.337 


0.674 


10.88 


14.98 


27.54 


0.247 


0.355 


0.710 


12.64 


17.61 


32.53 


0.258 


0.375 


0.750 


14.81 


20.78 


38.55 


0.280 


0.432 


0.864 


19.18 


28.57 


53.16 



Threads 

per 

Inch. 



27 
18 
18 

14 
14 
IlJ 
IlJ 
llj 
lli 
8 

8 
8 
8 
8 
8 
8 



Each length of pipe as sold is provided with a collar or 
coupling screwed on to one end and has a thread cut on the 
other end. Connections are made by screwing the threaded 
end of one pipe into the coupling on the other. There is no 
standard length of pipes, the range usually being from 16 to 
24 feet, with occasional short pieces. It can be ordered in 
lengths cut as desired for slightly extra prices; but it can be 
readily cut any length, and right- or left-handed threads may 
be cut as desired. It is quite malleable, and when heated may 
be bent into almost any shape by a skillful workman without 
materially changing the form of its cross-section. 

59. Pipe Fittings. — Fittings for connecting pipes and for 
giving them any required direction with respect to each other 
are regularly on the market. These fittings are mostly made 
of cast and malleable iron, the prominent exception being 
straight couplings with right-handed threads in both ends, 
which are usually of wrought iron. 



154 HEATING AND VENTILATING. 

Cast-iron fittings are generally preferred to those of malle- 
able iron in any system of piping for heating, for the reason 
that, being harder than the pipe and less elastic, they are not 
likely to stretch and yield sufficiently to permit leakage when 
the pipes are connected; if broken, a fracture can readily be 
detected and a new fitting supplied. Malleable-iron fittings 
frequently stretch if pipes are screwed somewhat too hard, so 
that future expansion and contraction is quite certain to cause 
a leak. If it is necessary to take down a long line of pipe 
in which no removable joints occur, a cast-iron fitting can be 
easily broken, thus often saving more time than the cost of 
the fitting, while the malleable fitting cannot be so disposed of. 
It is quite true that malleable fittings are stronger than cast- 
iron when of equal weight, but those on the market are much 
lighter than the cast-iron ones; and, moreover, the standard 
fittings are abundantly strong for any pressures likely to be 
sustained in ordinary systems of heating. 

The standard pipes are considerably stronger than the 
standard fittings, and if extra heavy pressures are required, 
say ICO to 150 pounds per square inch, it is advisable to use 
special fittings, which differ from the ordinary ones principally 
in weight. 

The fittings which are on the market can be divided into 
various classes, depending upon their use. 

For high pressure superheated steam, considerable trouble 
has been experienced with cast-iroix fittings. If cast-iron fit- 
tings are used for such purposes consideration should be given 
to this fact and precautions taken to prevent accidents from 
this cause. 

Pipe Connections. — For joining pipes in the same line there 
is provided, first, the wroughUiron coupling shown in Figs. 50 
to 52. 

The coupling, usually with plain exterior, has right-hand 
threads cut in both ends, and is used principally in erecting a 
pipe line where the construction is continuous from one end to 
the other. A reducing coupling, Fig. 52, is frequently used 
for uniting pipes of different sizes. In cases where it is neces- 



PIPE AND FITTINGS. 155 

sary to " make up " or unite lines of piping which come 
together from diflfercnt directions, a left-hand thread can be 
cut on the end of one of the pipes and the junction formed by 
using a coupling similar to the above, but with a right-hand 
thread cut in one end and a left-hand thread cut in the other, 
such a coupling being known as a right-and-left coupling. To 
use this coupling room is required for end motion of one of 
the pipes sufficient to insert it. 







Fig. so. Fig. 51. Fig. 52. Fig. 53. 

Coupling. Right-and-left Coupling. Reducing Coupling. The Union. 

In making up right-and-left couplings care must be taken 
that both threads on the pipe engage with those in the coup- 
ling at about the same instant. This can be done by screwing 
the coupling by hand on the end of each pipe, and counting 
the number of turns that can be made, noting the number of 
threads in sight after the joint is made up. This coupling, 
while sometimes difficult to use, forms the most certain method 
of imiting two pipe lines so that they will not leak. For join- 






Fig. 54. Fig. 55. Fig. 56. 

Section of Union. Flange Union. Long-threaded Nipple and Lock-nut. 

ing pipes a coupling which separates into three pieces, termed 
a union, is often employed. The parts of the union are 
screwed onto the ends of the pipe, and are drawn together by 
a revolving collar which engages with the thread on one of the 
pieces. The joint is formed either by drawing flat faces in the 
union against some elastic and soft material, as packing, or 
else by producing contact of ground and fitted metallic sur- 
faces. Pipes are also held together by screwing flanges to the 




156 HEATING AND VENTILATING. 

pipes, and drawing these flanges either in contact or against a 
ring of packing by bolts (Fig. 55). Such a joint is called a 
flange union. 

Lengths of pipe are frequently made up by a short piece 
of pipe with a long screw-thread cut on one end, onto which is 
screwed a very short collar or lock-nut, Fig. 56. The junction 
is made between two ordinary pipe couplings by first screwing 
the long thread into one pipe coupling until the piece is short 
enough to be slipped into position, then it is screwed into the 
other coupling by unscrewing from the first. When screwed 
home, the collar or lock-nut is turned tightly against the first 
coupling, forming a steam-tight joint either by metallic contact 
or by use of packing. 

Pipe Bends and Elbows. — For changing the direction of 







Fig. 57. — Qo® Fig. 58. — ^45® Fig. 59. — 90® Fig. 60.— Long- 

Cast-iron Elbow. Cast-iron Elbow. Reducing Elbow, radius Elbow. 

pipe lines there can be purchased elbows with bends of 45 or 
90 degrees, also reducing elbows in which one opem'ng is for 
smaller size of pipe than that of the other. The 90-degree 
dbow can be had either with right threads in both ends or 
with right and left threads, as required. The right-and-left 
threaded elbow can be used for making up two pipe lines in 
a manner similar to that described for a right-and-left coupling. 
The internal diameter of elbows is somewhat in excess of 
that of the external diameter of the pipe, and the radius of the 
bend is, according to Briggs' table (Van Nostrand Science 
Series, No. 68), equal in nearly every case to the diameter .of 
the pipe plus a constant which varies from f inch for the 
smallest size of pipe to ^ inch for the largest size. For the 
sizes of pipes used in heating the radius of curvature is prac- 
tically equal to that of the diameter of the pipe plus i inch. 



PIPE AND FITTINGS. 



157 



Where the friction caused by a standard elbow is detri- 
mental, special fittings (Fig. 60) can be obtained in which 
the radius of curvature is from two to three times that given. 




Reducing Tee — Openings Various 
Sizes. (Id describing state diam- 
eter o[ branch last.) 

Such httings are especially desirable in heating by hot-water 
circulation, and often permit the use of smaller pipes than would 
be possible with standard fittings- 




Pi^ Junctions, Tees, Y's, etc. — For the purpose of taking 
off one pipe line from another special fittings can be had, 
which are designated, according to their shape, as tee, cross, 





side-outlet elbow, and Y-hratick, all of which can be bought 
with the openings for the same or different sized pipes in any 
combination required. 

These various fittings are shown in the annexed engravings. 



HEATING AND VENTILATING. 



Miscellaneous Fittings. — For reducing the size of opening 
in a fitting, bushings of cast ("Fig. 69) or malleable iron can be 
used; for dosing up the end of fittings a screwed plug (Fig. 70) 
can be employed; and for dosing the end of a pipe a screwed 
cap (Fig. 71) can be used. Where a coil of pif>e is desirable, it 



Fig. 6g. — Bushing. 



I 



• fl^O 



Reiuni Bends. Offset. IxKk-nut. 

can be formed by screwiog pipes into U-shaped fittings, called 
return bends. These can be had with either right threads or 
right-and-left threads, and in dose (Fig. 72) or open pattern 
(Fig. 73), and with the threads tapped so as to give nearly any 
pitch or rake of the pipe. For slightly changing the poation 
of a pipe an oETset (Fig. 74) can be used. To prevent leaking 
where a long-threaded nipple has been used, a lodt-nut can be 
screwed on against a grummet, or ring of packing. 

Fittings can also be had for erecting parallel Unes of [H] 



be . 



I 



FlG. 76.— Branch Tee, Plain. Fio. 7;.— Branch Tee, with Back Outlet. 

as shown in Figs. 76 and 77; they are termed brawh tees, and 
can be had for almost any number of pipes, and for sizes 
varjing from three-quarter to three inches. The distance 
between centres of branches is varied somewhat, but is usually 
2 inches for three-quarter-inch pipe, 2J inches for one-inch 




PIPE AND FITTINGS. 



159 




Fig. 78. 

Shoulder 

Nipple. 



\\\v\\\\\v\( 



Fig. 79. 

Close 

Nipple. 



pipe, 3 inches for one-and-a-quarter-inch pipe, and 3I inches 
for one-and-a-half-inch pipe. The branch tees are fitted with 
opening for supply-pipe and discharge-pipe either in end or 
side as spedfied. In those made for circulation the holes are 
tapped with right-hand threads; those made for 
box-coils are tapped for left-hand thread on 
branches. 

Short pieces of pipe called nipples can be had 
of any length required, provided with right-hand 
threads cut on both ends, or with right thread 
on one end and left thread on the other. Short 
pieces of pipe called quarter or eight-bends (Fig. 
no) may be used in place of elbows when a 
long-radius turn is required. 

In addition to the fittings mentioned there can 
be had, for supporting the pipes to side walls, 
hooks and hook-plates with curved or straight arms, ringed 
plate, and coil-stand, as desired. 

There can also be had hangers of various patterns for sup- 
porting and holding pipes from ceilings. These are of great 
variety of pattern, and are made so that, if desired, they can 
be put on after the piping is in place. 

The principal standard 
fittings as above described 
are also made of brass. 
Fro. 80.— Hook-plate. Ceiling and Floor ^Plates 

are collars used to hold the 
pipes in place, and to pre- 
vent overheating of wood- 
work by the steam or hot 
Fig. 81.— Expansion-plate. water. These are often 

made in halves, which may 
be slipped on over the pipes, and are fastened to the woodwork 
by screws, thus holding the pipe in position and keeping it 
from contact with wood. 

60. Valves and Cocks. — ^The fittings used for the purpose 
of stopping the passages in pipes are operated by moving 




JLULLUL 




Fig, 83.— Coil-stands. 



160 HEATING AND VENTILATISG. 

a disk across the pipe with or without rotation, or by simply 

turning through an angle. The first class have been generally 

called valves, the second cocks. 

Valves are of two classes: the globe valve (Fig. 85), which 

closes an opening in a dia- rr»i , ^»ii n ^ 0^ 

phragniimraUeltothedirec- £^C^J^^j£X 

tion 01 How, and the gate 

valve (Fig. 84), which closes 

an opening at right angles 

to the pipe. 

The globe valve forms a 

serious obstruction, since 

any fluid in passing through 

it must make two turns, each nearly a right angle; while 

the gate valve when open presents little or no resistance- 

The globe valve is much more simple in construction than 

the gate valve, is cheaper, and often will answer all require- 
ments for steam-heating, but will 
seldom do for hot-water heating. It 
should be set so that the valve closes 
against the flow; when set in the 
opposite way accidents might happen 
—for instance, if the valve should be 
detached from the stem it could not 
be opened, although the stem would 
move apparently all right. It will be 
noted that the diaphragm of the globe 
valve forms an obstruction in the 
pipe, which extends to the centre, 
and if the stem of this valve be set 
vertical when used for a horizontal 
pipe it is likely to cause the pipe to 
stand half full of water. Whenever 
used in steam-heating, on a horizon- 
tal pipe, the stem should be [daced 

in a horizontal portion, so that it will not interfere with I 

drainage of water of condensation from the pipe. 




Fig. 84.~Gate VUve, 




PIPE AND KllTINGS. 



161 



The construction of the gate valve varies in detail as made 
by different manufacturers, but it in general consists of a gate 
which is moved across the opening in the pipe by turning the 
stem. When the gate reaches the bottom of the pipe it moves 
laterally sufficient to bring a strong pressure on the seat. 




ih Disk Seal. 



j These valves are made with a stem which rises with the gate 

r with one which remains in one position, the gate travelling 

up the stem (Fig. 84)- This latter form is objectionabie, as 

one cannot tell, by looking, whether the valve is open or dosed. 

Globe valves are made with a solid metallic seat, or with 

, a seat made of soft metal or packing, as in Fig. 85, of such 



162 



HEATING AND VENTILATING. 



a foim that it can be replaced whenever the valve begjns i 
leak. 

Angle Valves {Fig. 86) are made in the same general way' 
as globe valves, except that the openings are at right angles to 
each other. They cause a slightly greater resistance to motion 
than the ordinary elbow, but not suffident to prevent thrir i 




use for any system of heating. The seats are either meta 
or of soft material, wWch can be removed. 

Stuffing-boxes. — In all classes of valves a ca\'ity is left around 
the stem, which must be filled with some packing material by 
turning back a cap-screw. Hemp, lamp-wicking, asbestos fibre, 
well oiled and, if possible, covered with plumbago, will make 
satisfactory packing for tius purpose- Patent ring packing 



PIPE AND FITTINGS. 163: 

can be purchased, usually made of asbestos fibre soaked in <nl, 
and serves an excellent purpose. 

Radiator Valves. — These are forms of angle valves with 
fittings making them especially convenient for radiator connec- 
tions, being plain as shown in Fig. 87 or with an attached 
union as in Fig. 88. These are often nickel-plated. 

Radiator valves for hot water, when closed, have a small open- 
ing left to allow for the expansion and contraction of the water. 

The various kinds of valves which have been described are 
made with sockets for screwed connections to the pipes, or 
mth flanges which are to be bolted to amilar flanges screwed 
on the pipes as desired. They can also be 
had, especially for the larger sizes, with either 
brass or iron bodies. 

Cross Valves. — A form of angle valve with 
one supply and two opposite discharge open- 
ings is sometimes convenient, and is termed 
a cross valve- {See Fig. 99.) 

Corner Vakes, in which the openings are 
at the same level but at right angles, can be 
purchased if desired (Fig. 89). 

Cocks.— A plug, slightly conical, pro\nded judLwr Valve, 
with one or more ports or holes through it, 
and arranged so that it can be turned in any direction, is 
termed a cock. When there is but a single hole it is called a 
plain cock. When two or more holes at angles to each other, 
it is called a two-way or three-way cock, ance water can be 
directed in two or more directions by varying the angle 
through which the plug is turned. Cocks are verj- little used 
in steam -heating; as ordinarily made they are apt to leak, and, 
besides, do not provide a full opening for the fluid (Fig. 95). 

Improved cocks with larger openings and with packed ends 
are now much used on the blow-off pipes from boilers, and are 
for this purpose superior to valves. 

Quick-opening valves (Fig. 91I for use on hot-water pipes 
are often made on the same plan as cocks, and do excellent 
service in these places. 




HEATING AND VENTILATING. 




PIPE AND FITTINGS. 



165 



A 



— Union Elbow. 



Check Valves. — Where it is necessary that the flow should 
always take place in the same direction and there is danger 
of a reverse flow, check valves are employed. These are usually 
of a similar pattern to the globe valve, the seat being at right 
angles to the direction of flow, with either a flat or ball valve 
(Figs. q6, 97). In this class the valve 
is held in place by its own weight or 
by the weight of the fluid in case of 
reverse flow. They are made for hori- 
zontal pipes, vertical pipes, or angles. 
One known as the swinging-check valve, 
in which the seat is at an angle of 
about 45 degrees to the direction of 
flow ( Fig. 98) , offers less resistance 
to the fluid, and is generally to be 
preferred. 

61. Air-valves. — It is necessary to provide means for allow- 
ing the air to escape in systems of steam and hot-water heating. 
Air is heavier than steam, and although 
it will mix with it to a great extent, it 
will finally settle at or near the bottom 
of a radiator or pipe filled with steam. 
Air is, however, much lighter than water, 
and it will gather in any bends that are 
convex upward and in the upper part of 
radiators filled with water, and unless 
removed it will prevent circulation. 

For removal of the air several forms 

of valves and cocks have been especially 

manufactured. These are usually made 

Plug-cock. 01 i" or g-mch pipe size, and vary in 

quality and design from the simplest valve 

to be opened by hand to a complicated automatic pattern, 

which permits the escape of air, but not of water or steam. 

One of the simplest patterns of air-valves is shown in Fig. 

This can be had with a bibb if desired, also with various 

forms of handles or keys, and with nickel or brass finish. 




HEATING AND VENTIl^TING. 




##§ 




BomonUl Check Angle Check Vali-c Vertical Check. Sleam Cock 

Valvt. Flnnged Ends. 




ErpaDsioa or Slip Joint. Sleaja Cock, Screwed Ends. 

Fig. 90. — Principal Valves and Stops used in Heating- 



PIPE AND FITTINGS. 



167 



Automatic air-valves are made of a great variety of pat- 
l:tems. Those for steam-radiators are all closed by the expan- 
Lsion of some material. Fig. loi shows an expansion air-valve, 
lin which the valve is closed by the expansion of a curved 
I metallic strip. The valve will remain open until this curved 
Istrip becomes neariy equal in its temperature to that of the 
■ steam; the heat then increases its length and it bends out 



1^ 




I sufficiently to close the valve. A drip-pipe is provided for 
L removing any water of condensation escaping from the air- 
( valve. 

Another form, which has in the past been extensively used, 
Fis shown in Fig. 102. In this case the interior tube A is heated 
[ more than the frame hb\ this serves to press the valve c against 
I the end of the tube when it is heated, thus closing the orifice. 
I This is best adapted for use in a vertical position. 

A form of air-valve now in extensive use is shown in Fig. 



168 



HEATIXG AND VENTILATING. 



loj. In this a composite material which expands rapidl 
whea heated is used instead of metal. It is claimed for some a 
these valves that with suitable adjustment of the inside screi 
the temperature of the radiator will be automatically maiai 
tained at any desired point! 
— a mixture in any required 
proportion of air and steam 
being maintained in the radi- 
ator by this action. 

To prevent escape of waM 
and injur;- to furniture 
radiator-valve with 
attachment is often used, t 
shown in Fig. 104, The" 
valve is closed when heated, 
as in Fig. 103. by the expan- 
sion of a composite sub- 
stance; it is connected to a 
float, so that if water passes into the air-valve the float will 
rise and close the orifice regardless of the temperature. 
An automatic air-valve for hot-water radiators is si 






the sketch, Fig. 105. The air escapes at A, the orifice bdojr 
dosed by the float F acting on the lever L. So long as only 
air surrounds the float it sinks and keeps the orifice open, but 
as soon as water surrouods it it rises and doses the orific& 



PIPE AND FITTINGS. 



169 



Fig io6 shows a modern pattern of float air-valve. The 
floating element of this valve has such a short vertical travel 
that it will expand and dose the valve tight when heated by 
contact with steam. These valves close and prevent the 
escape of both steam and water. A float valve with a siphon 
to return the excess water to the radiator and prevent the 
drowning out of the float is shown in Fig. 107. 

62. Expansion- joints. — In the erection of any system of 
piping means must be provided so that the elongation of the 





Fic. 106 . Fill. to8. — Flanged Expam^on-joioL 

jHpe due to expan^on will not cause a leak. For all ordinary 
purposes of heating the expansion can be provided for by the 
use of elbows and right-angled offsets, of such length that the 
expansion will simply cause one pipe to unscrew slightly in 
one or more joints- This requires the use of two or three 
dhows, and so causes a slight increase of resistance to flow due 
to friction; but it is a very satisfactory arrangement, and will 
stand for years without developing leaks, even with high- 
[ ^ffessure steam, if properly erected. 



170 



HEATING AND VENTILATING. 




Fig. log. — Bundy 
Elastic Coupling. 



The expaimon of wrought iron is one part in 149,000 of 
length per degree F. The expandon of cast iron is somewhat 
less and varies between one part in 168,000 and one part in 
180,000 of length per degree F., depending upon its composi- 
tion. The expansion of steel is inter- 
mediate between that of wrought iron 
and that of cast iron; it varies between 
one part in 149,000 and one part in 
162,000, The greatest expansion, that of 
wrought iron, is equivalent to about 
1.45 inches per 100 feet length in chang- 
ing from temperature of freezing to boil- 
ing, or nearly ij inches per 100 feet of 
length. 
As it is impossible to confine this expansion without buckling 
the pipe or breaking the fittings, the piping has to be erected 
with bends, offsets, or expansion-joints, so situated as to pro- 
vide enough flexibility to take up the expansion. Where there 

a XT 

Fig. no.— Right Angle and Offset Bends. Fic. ii:.— Expansion Bend. 

is sufficient room, pipe bends provide adequate means of taking 
up the expansion. Bends can be made or obtained to nearly 
any radius not less than six times the pipe radius and for any 
number of degrees. 

Pipe bends increase the resistance to the flow of water or 



PIPE AND FITTINGS. 171 

steam but little more than straight pipe, and the saving in 
friction head would often warrant their use without consider- 
ation of the eflfectiveness in taking up expansion. The use 
cuts down the number of joints, over all the other- devices. 
For exposed piping in heating and ventilating their use is often 
awkward from an architectural standpoint, as piping usually 
run with or near the lines of the room, that is either vertically 
or horizontally. 

Long lengths of pipe should be supported on rollers or 
swinging hangers so as to freely transmit the expansion to the 
bends, expansion-joints or offsets, which should be provided 
to take up the expansion. 

Expansion-joints are often used constructed of copper pipe 
in form of a U-shaped bend; also of one or more diaphragms 
connected to each other at the edges and to the pipes near the 
centre (Fig. 109). The copper bend is always satisfactory. 
The last-named device works very well if means can be adopted 
to thoroughly drain ofiF any water lodging against the dia- 
phragm. If used in a horizontal position, and on large pipes 
it is likely to gather sufficient moisture to form a water-hammer 
that may produce rupture when steam is turned on. 



CHAPTER VII. 
RADIATORS AND HEATING SURFACES. 

63. Qualities of an Efficient Steam Radiator. — The efficiency 
of a steam radiator is primarily dependent upon the temperature 
of the surface and upon the facility for utilization or abstrac- 
tion of the heat which passes through its walls. In order to 
produce uniform temperature internally, it is necessary to 
abstract the air from the steam, which is facilitated by a positive 
and rapid circulation of the steam in all parts of the radiator. 
The water of condensation should also be removed since its 
temperature is likely to fall below that of the steam and it also 
produces poimding or water hammer. The presence of air, a 
condition known as " air binding," is the principal reason for 
uneven or partial heating of the radiator. The removal of 
the air is greatly facilitated by circulation of the steam. 

The absorption of the heat transmitted through the walls 
of a radiator requires favorable conditions for radiation and 
convection. The construction should be such as to intercept 
as little as possible the radiant heat and induce as far as 
possible air-currents over the radiator which should absorb the 
heat from the surfaces, the absorption by convection being a 
function of the velocity. The amount of heat which will pass 
through various kinds of radiating surface is determined largely 
by experiment, and has been fully discussed in Chapter IV. 
In this chapter we will consider briefly the methods of con- 
struction. 

64. Radiating Surface of Pipe. — Very efficient radiating 
surfaces can be made of coils of piping arranged as shown. 
The return-bend coil shown in Fig. 112 is made by connecting 

172 



RADIATORS AND HEATING SURFACES. 173 

return-bends with lines of straight pipe. The pipe mostly 
used is one inch in diameter, although, when the bends are 
numerous, i^- or 2-inch pipe should be used to reduce the fric- 
tion. In use the flow is continuous, the fluid entering at the 
top and thence with a gradual descent flowing to the right 
and left alternately, finally discharging at the bottom. There 
is a great deal of friction in coils of this class, and air is likely 
to gather in the bends and stop circulation. The writer would, 
therefore, recommend that they be employed only when other 
forms will not answer. 

The branch-tee or manifold coil is constructed by connect- 
ing branch-tees with parallel lines of pipe. In each pipe-line 




Fig. 112. — Return-bend Coil. 

one or more elbows must be placed to counteract the effect 
of unequal expansion. 

The coil may be arranged on a flat wall-surface so as to 
form a milre branch- tee coil as in Fig. 113, lower part, or with 
both branch-tees at one end and elbows and nipples at the 
opposite end; the fittings at ends being connected by pipes 
having the proper pitch. Such a construction is called a return 
branch-tee coil, see upper part Fig. 113. The coil may be 
arranged on two sides of a room with the elbows placed in the 
intervening comer, in which case it is called a corner coil. 

The various types of branch-tee or manifold coils as de- 
scribed present small frictional resistance to the flow of steam 
or water and give satisfactory service for either steam or hot- 
water heating. 



174 



HEATING AND VENTILATING. 






U two connections are used the steam should be supplied 
at the highest point of the coil, and the return taken off at 
the lowest; if one connection, steam is to be supplied at I 




id Retum-foil. 

lowest point. The horizontal portion should be given a pitc 
of one inch in ten or twelve feet, and an air valve or cock should 
be connected to each coil. When several retum-bend coils 




are grouped together, as in Fig. 114. the construction is termed 
a box coil. This has all the faults in an aggravated manner 
that were ascribed to the return-bend coU, and in addition 
causes a loss of efficiency due to close grouping of surfa< 



RADIATORS AND HEATING SURFACES. 175 

65. Vertical Pipe Steam-radiators. — These were at one 
I time used extensively, and were made by screwing short pieces 
of vertical pipe into a cast-iron base and connecting the pipes 
in pairs at the top with return-bends. One form was made by 
screwing pipes, having the upper end closed and provided with 
an internal diaphragm, into a cast-iron base, the diaphragm 
being so placed as to produce the same circulation in one pipe 
tthat was obtained in two pipes with the other form. 




Fic. 115.— Pipe Radiator. 

The pipes are arranged in two or more rows as necessary 

to secure the desired radiating surface. An air-valve must 
always be provided with these radiators, the best location for 
"Which is at about one-third the height of the radiator, and on 
the end opposite the admission. 

The wiought-iron radiator is constructed in nearly every 

C'ase of one-inch pipe, taken of such length that there is one 

square foot of exposed radiating surface for each pipe in the 

^■3<diator. The form being quite regular its surface can be 

urately measured. 



176 



HEATING AND VENTILATING. 



66. Cast-iron Steam-radiators.— Cast-iroa sectional 
tors are now mostly used in direct heating. 

Those principally used have vertical radiating surfaces;' 
and are made by connecting a series of parallel vertical sections 
by nipples screwed (rom the outside or inside of the base. The 
sectional radiators can be increased or diminished in length by 
adding or taking off sections. The greater portion of those of 
recent design have a plain surface depending on their form alone 
for any esthetic effect. The following illustrations give a very 
fair idea of the appearance of those in use. They are painted 




— WhiUicr Extended Surface Radiator. 



in various colors, enamelled or bronzed, as may be required 
by the house owners or architects. 

The efficiency of direct radiation is somewhat increased 
painting or bronzing, but is lessened by varnishing or enam- 
elling; but that of indirect is not so affected. 

These radiators are made in great ^'ariety of forms, and can 
be had of such shape as to surround columns, or fit in comers; 
and of almost any height desired. Some of the radiators are 
fitted with warming closets. 

The sectional radiators are in many cases built in such a, 
manner as tn form flues for the passage of air from the botl 



red 



RADIATORS AND HEATING SURFACES. 



177 



to the top of the radiator for the purpose of increasing the air- 
heating capacity. Such radiators are termed fitie radiators. 

Radiators are sometimes built with projecting fins or orna- 
ments of cast iron for the purpose of greatly extending the 
surface in contact with the air. Such a radiator is termed an 
extended surface radiator, and is now little used for direct heat- 
ing (Fig, ii6). 

The radiators in principal use are constructed as described, 




but radiators have been built by many other methods and in 
many other shapes. They have been constructed of one solid 
casting, and by uniting sections of various forms by bolts and 
packed joints. 

67. Hot-water Radiators. — Hot-water radiators differ essen- 
tially from the steam-radiators in having a horizontal passage 
at the top as well as at the bottom. This construction is neces- 
sary in order to* draw off the air which gathers at the top of 
each loop or section. Aside from this the construction may 



178 HEATING AND VENTILATING. 

be the same in every particular as that for steam-radiators; 
in general the hot-water radiator will be found well adapted 
for steam circulation, being in some respects superior to the 
ordinary form. 

Many of the hot-water radiators, as shown in Fig. 117, 
are made with an opening at the top for the entrance of water 
and at the bottom for its discharge, thus insuring a supply of 
hot water at the top and of colder water at the bottom. 

Some of the hot-water radiators are constructed with a 
cross-partition so that all water entering passes at once to the 
top, from which it may take any passage toward the outlet. 

The hot-water radiator, is, however, usually made ^ith 
continuous passages at top and bottom, and the warm water is 
supplied at one side and drawn ofiF on the other. The action 
of gravity is depended on for making the hot and lighter water 
pass to the top and the cold water to sink to the bottom and 
flow off in the return. 

Wall Radiators, — Cast-iron wall radiators are extensively 
used. Several different designs of these wall radiators and 
their installation are shown by the following illustrations. 
A space of about two inches should be left between the radiator 
and the wall from which it is supported. As the thickness of 
the wall radiators rarely exceeds three inches, the total distance 
from the wall is usually not over five inches, with a maximum, 
seldom exceeded, of six inches, their saving of space is consider- 
able. They can be hung from any unoccupied wall or even 
ceiling space, without sacrificing either their eflSciency or their 
appearance. 

The units are furnished in rectangular shapes and tapped 
to be used with the longest dimension either horizontal or 
vertical and for any system of piping. The units usually con- 
tain 5, 7 or 9 square feet of heating surface although several 
other sized units can be obtained. By a proper grouping 
of the units the desired radiating surface can be obtained in a 
manner more economical, more convenient, and more effective 
than with pipe coils. 

One type of wall radiator has two sets of intermediate cross 



RADIATORS AND HEATING SLRFACE8. 179 





FlC. iiS.—One-L-oluinr Kadialor. Fic. j 3o.— Three- column Riulial 



\ 




I Fic. 119. — Two-column Radiatur. Fic. ui. — Four-column Radiator. 



RADIATORS AND HEATING SURFACES. 



181 



tubes running at right angles to each other so that when installed 
either in a horizontal or in a vertical position, it provides for 
the direct passage of the wet steam and the water of conden- 
sation to the lowest tube, from which it is readilv drained. 




S.— Diagram Shnwivig Wall Radiator L'nils Assembled. 



It is claimed for this type (Fowler and Wolfe) that four 
square feet of heating surface can be installed on one square 
foot of wall surface. Special requirements such as for use in 
pla.te warmers, comer radiators, and bay window radiators can 
be met by tapping the radiator units at the necessary angles. 



18S 



HEATING AND VESTILATING. 



Pressed J?adi(i/(jr J.— Radiators made of thin pressed stM 
are sold to a limited extent on the market. These radiatoifl 
come already assembled. Their durability as compared witibfl 
cast-iron radiators, has not as yet been fully established. 

68. Direct-indirect Radiators.— Radiators arranged witll 
a damper under the base and located so that air from the out- 1 
ade will pass over the heating surface before entering the rooml 
are often used to improve the ventilation. The surface of thes 



radiators should be about 25 per cent greater than that of &J 
direct radiator for heating the same space. The styles and] 
kinds either for steam or hot water are the same as the direct T 
6<>. ladirect Heaters. — Radiators which are employed to ] 
heat the air of a room in a passage or flue which supplies air 
are termed indirect. These heaters are made in various forms, 
either of pipe arranged in return bend or in manifold coils, 
as in Fig. 113. or of cast-iron sections of various forms united 
in different ways. When cast-iron surfaces are used, they aie i 



RADIATORS AND HEATING SURFACES. 183 

generally covered with projections like the extended surface 
radiator. The sections, or, as they are sometimes called, the 
stacks for indirect heating, are usually held together by bolts. 
The joints being formed by inserting packing between faced 
surfaces. The sections are sometimes united by nipples screwed 
into branch-tees above and below, as shown in Fig. 128. which 
is an excellent form for hot-water circulation. 




I P[pc Coil. 



Indirect radiators should be placed in a chamber or box as 
nearly as possible at the foot of a vertical flue leading to the 
room to be heated. 

Air is admitted through a passage from the outside pro- 
vided with suitable dampers to a point beneath the indirect 
stacks. It is taken off generally on the opposite side, and 
directly into the flue leading into the room to be heated. 

The chamber surrounding the indirect radiator is usually 



184 HEATING AND VESTILATISG. 

built of a casing of matched wood, as in Fig. 130 and Fig. 131, 
suspended from the ceiling of the basement, and lined inside 
with bright tin ; but a small chamber of masonry at the bottom 
of a flue is a better and more durable construction. The flue 
leading from the chamber is of masonry or gahanized iron; 
that supplying the cold air, of matched wood and sheet iron. 
There should be a door in the chamber so that the indirect 
heater can be examined and cleaned when required. It is often 
of advantage to ha\'e a passage and deflecting damper so ar- 
ranged that air can be drawn into the room for ventilation 
without passing over the heater. 




Fic, 1J0, — Arrangement of Indireci Healer. 

The registers for admitting the heated air into the rooms 
can be located as desired, either in the walls or the floor; for 
ventilation puqx>ses it is preferable to admit the air near the 
ceiling, and as shown in Fig. 132. Registers in the floor should 
be protected from the falling dirt. 

Seliing of Indirect Healers. — The indirect heating-surface is 
supported usually by bars of iron or pieces of pipe held in place 
by hangers fastened at the ceiling (Fig. 130). This heater 
should be set so as to give room for the freest possible circula- 
tion of air, and so that all parts will be at least ten inches from 
top or bottom of casing, and arranged so that no air can pass 
into rooms without being warmed. An automatic air-valve 
should be used to remove the air from the sections of the heater. - 



RADIATORS AND HEATING SURFACES. 



185 



If the sections are of proper lorm, one connection will be 
sufficient for steam; but in nearly every case two connections, 
one for the supply and one for the discharge, will be required 
for water circulation. 

70. Proportions of Ports of Radiators. — There is great 
difference regarding the relative volume of radiators of differ- 




Fic, 131. — Arrangement of Indirett Fic, 132. — Indirect Heater Arranged 

Healing Surface. for Ventilation. 



ent make as compared with the surface; but the practice is 
quite uniform as regards the sizes of supply-pipes for either 
steam or hot water. Because of the high efficiency of a radiat- 
ing surface formed of one-inch horizontal pipe, it has been 
argued that this should form a standard for relation of contents 
to surface. It is seen, however, by consulting the tests given 
in Chapter IV, that inch-pipe vertical radiators are not more 
efficient than cast-iron radiators with larger volume; so that 
it is doubtful if the relative ratio of volume to surface is of 
importance. 



186 



HEATING ASD VENTILATING. 



It is of importance that the steam or water should circulate 
through the radiators with the least possible friction, and that 
in the case of steam-radiators the base should be of such a form 
as to perfectly drain; otherwise the water which remains in will 
be certain to cause the disagreeable noise and pounding known 
as water-hammer. 




I 



The following table gives the standards which are almost 
universally adopted by the different makers for the size of inlet 
and outlet to the direct radiators; those for indirects are to be 
taken one size larger: 



H 







^ &,"??*"■ 


Two Opealnoi. 


OacOp«d.«. 


oto 50 
20010300 


I inch 
ilinchea 
I* ■' 


■i ;; 
I) " 



CHAPTER VIII. 
STEAM-HEATING BOILERS AND HOT-WATER HEATERS. 

71. General Properties of Steam — Explanation of Steam- 
tables. — Steam has certain definite properties which always 
pertain to it and distinguish it from the vapor of other liquids 
than water. 

Steam, at any given pressure above a vacuum, pK)ssesses a 
definite temperature. The atmospheric pressure is difiFerent at 
different localities and for difiFerent conditions of the weather, 
thus causing slight changes in temperature of the boiling-point. 
The pressure which is read by any steam-gauge is that in 
excess of the atmosphere; the pressure which is given in the 
steam-tables is that which is reckoned from a perfect vacuumy 
and is usually called absolute; hence, in order to use the steam- 
table which is given in the back of the book, the pressure as 
determined by a steam-gauge reading must be increased by 
the atmospheric pressure. The atmospheric pressure is given 
accurately by a barometer, but it will be sufficiently accurate, 
for most cases, to consider it as 14.7 pK)unds. To use the 
table add this quantity to the gauge-reading and the result 
will be the absolute pressure. For approximate purposes the 
atmospheric pressure may be considered as 15 pounds. The 
steam-tables referred to give, in the first column, the pressure 
above a vacuum ; in the second column, the temperature Fahr- 
enheit; in the third, the heat, expressed in heat-units, required 
to raise one pound of water from zero Fahrenheit to the re- 
quired temperature. If the specific heat of water were unity 
at all temperatures, the heat contained in one pound of water 
would be numerically the same as the temperature. The 
difference is not great in any case. 

187 



188 HEATING AND VENTILATING. 

The fourth column gives the value in heat-units of the 
latent heat of evaporation for each pound of steam. This 

quantity expresses the amount of heat which is stored, with- 

* 

out change of temperature or pressure, during the physical 
change of condition from water to steam; and it has been 
termed latent because it cannot be measured by a thermometer 
(see Chap. I). It will be noted that this quantity is relatively 
large as compared with the sensible heat. It is of importance, 
since it expresses the amount of heat which is contained in one 
pound of steam in excess of that in one pound of water at the 
same temperature. 

The fifth column gives the total heat contained in one 
pound of steam; this is the sum of the sensible and latent 
heat. 

The sixth column gives the weight in pounds of one cubic 
foot of steam for various pressures. The steam-tables are 
arranged so as to give the heat in one pound of steam above 
32° Fahr., the freezing-point of water, instead of above zero. 

It should be noted that the temperature of steam corre- 
sponding to different pressures, as given in column (2), is also 
the boiling-point of water corresponding to the same pressure. 

As the temperature and absolute pressure of steam always 
bear definite relation to each other, it is quite evident that 
a steam-table could be arranged giving the properties of steam 
from measurements of temperature. This is generally not so 
convenient as the present arrangement. If temperatures 
are known, the corresponding pressure can be determined by 
inspection and interpolation in the present table. 

72. General Requisites of Steam-boilers. — The steam-boiler 
is a closed vessel, w^hich must possess suflScient strength to 
withstand the pressure to which it may be subjected in use; 
but it may have almost any form, and may be constructed of 
various materials. 

It is used in connection with a furnace, from which the heat 
required for evaporation is obtained by combustion of fuel. 
The heat is received on the surface of the boiler, and passes 
by conduction through the metallic walls to the water or 



STEAM-HEATING BOILERS— HOT- WATER HEATERS. 189 

steam. The surface which receives this heat is called heating 
surface, and is partly situated so as to receive the direct or 
radiant heat and partly located so as to receive the convected 
or indirect heat from the gases only. The heating surface in 
most modem boilers is made relatively great, as compared with 
the cubic contents, by the use of tubes containing water or 
heated gases, or by subdividing the boiler so as to make the 
surface large with respect to the cubic contents and weight. 
The steam generated rises in the shape of bubbles through 
the water in the lower part of the boiler, and is liberated from 
the surface of the water at the water-line. 

The power of the boiler depends upon the amount and 
form of heating surface, upon its capacity for holding water 
and steam, and upon the extent of fire-grate surface. Its 
economy depends upon the relative proportions of these, and 
the character and amount of fuel burned. Its ability to pro- 
duce dry steam depends upon the circulation of its liquid con- 
tents, and also upon the extent of surface at the water-line. 

For safety, the boiler must be provided with a safety-valve, 
and pressure and water gauges. For convenience automatic 
damper-regulators, water-feeding apparatus, etc., are desirable. 

73. Boiler Horse-power. — As a boiler performs no actual 
work, but simply provides steam for such purposes, a boiler 
horse-power is entirely an arbitrary quantity, and may be 
transformed into a lesser or greater amount of work, as the 
character of the engine which uses the steam varies. 

The standard established by the Committee of Judges at 
the Centennial Exhibition in 1876 as a boiler horse-power has 
been universally adopted, and would, no doubt, in absence 
of other stipulations, constitute a legal standard of capacity. 
This committee defined a boiler horse-power as the evapora- 
tion of 30 pounds of water from feed-water at 100° Fahr. into 
steam at 70 pounds pressure; this is equivalent to the evapo- 
ration of 34.5 pounds of water from a temperature of 212° 
Fahr. into steam at atmospheric pressure.* Engines require 

* The condition of evaporating from water at 212" into steam at the same 
temperature will be referred to hereafter as evaporation^ without other qualification. 



190 HEATING AND VENTILATING. 

from 12 to 40 pounds of steam per horse-power per hour, 
depending upon the grade or class to which they belong; hence 
the steam required to perform one horse-power of work in an 
engine bears no definite relation to a boJler horse-power. 

Since the evaporation of one pound of water from and at 
212° Fahr. requires 966 heat-units, one boiler horse-power is 
equivalent to 33,327 heat-units. 

For heating purposes a more convenient standard of power 
is the square foot of radiating surface. Each square foot 
of direct steam-radiating surface gives ofiF 220 to 280 heat- 
imits per hour when the difiFerence of temperature is 150 degrees 
which is that usually existing in low-pressure steam-heating. 
About two-thirds as much is given off by one square foot of 
hot-water radiating surface. As the evaporation of one pound 
of water requries 966 heat-units, there is needed about one- 
third of a pound of steam for each square foot of steam-radia- 
ting surface per hour, hence one boiler horse-pK)wer will be 
sufi&cient to supply somewhat more than 100 square feet of 
direct radiating surface; that is, we can consider the boiler 
horse-power as equivalent to 100 square feet of direct steam 
radiation, with sufficient allowance to meet ordinary losses. 

74. Relative Proportions of Heating to Grate Surface. — The 
relative amount of grate surface and heating surface required 
in a steam-boiler depends, to a large extent, upon the nature 
and amount of coal burned per unit of time. That part of 
the heating surface which is close to the fire and receives 
directly the radiant heat is much more efiFective than that which 
is heated by contact with hot gases only; but it will be found 
that considerable indirect heating surface will in every case 
be required, in order to prevent excessive waste of heat in the 
chimney. Power-boilers have been rated for a long time not 
on their actual capacity, but on the amount of heating surface; 
and this quantity as well as grate surface is an important con- 
sideration for heating-boilers. It is the general practice to 
consider 10 square feet of heating surface in water-tube boilers 
or 15 square feet in plain tubular boilers as equivalent to one 
horse-power. 



STEAM-HEATING BOILERS— HOT- WATER HEATERS. 191 

The actual power of the boiler depends more upon the 
method and management of the &res than upon the size; and 
either of the above classes of boilers can be made to develop 
under favorable circumstances from two to three times the 
capacity for which they are rated. 

A rating of 15 sq. ft. of heating surface to one horse-power 
requires an evaporation of 2.3 lbs. of water per square foot of 
heating surface per hour, and a rating of 11.5 sq. ft. per horse- 
power requires an evaporation of 3 lbs. Experience for a 
number of years with power-boilers — 20 horse-power and 
larger — indicates these proportions to be safe ones and to result 
in durable construction. With the small boilers often used in 
house-heating the waste due to loss of heat from the heating 
surfaces, unperfect combustion, and b^d management generally 
are much greater, so that it is necessary to use boilers some- 
what larger than would be required by the data given. 

The house-heating boiler, however, under best condition of 
management and draft will give, as shown by actual test, results 
approximating very closely to those obtained with the pK)wer- 
boiler under best conditions. In the ordinary management 
of heating-boilers the principal loss is due to operating with 
an insufficient supply of air, hence to secure best results the 
draft should be so arranged that whenever the air supply below 
the grate is reduced an amount sufficient to prevent perfect 
combustion, air should be admitted above the fire. 

With perfect combustion and no waste of heat, one pound 
of pure carbon would evaporate about 15 pounds of water, but 
as all coal contains considerable ash and refuse, and further- • 
more as an amount scarcely ever less than 25 per cent of the 
total heat must escape into the chimney, the results obtained 
in practice are much less and seldom exceed an actual evapo- 
ration of 9 pounds of water for each pound of coal. 

The amount of coal burned per square foot of grate per 
hour varies in large power plants with varying conditions of 
the fuel and the draft from 15 to 30 pounds, but under usual 
conditions of house-heating boilers it varies from 4 to 8 pounds 
per hour. 



192 HEATING AND VENTILATING. 

The amount of heat absorbed by the boiler heating surface 
depends upon the circulation of the heated gases, the circula- 
tion of the water and the difference in temperature between 
the gases and the water. The average absorption in power 
boilers varies between 2000 and 3000 B.T.U. j)er square foot 
per hour and the ratio of grate to heating surface varies between 
I to 40 and I to 60. With house-heating* boilers either for 
water or steam it is probably not desirable in the interests of 
economy to require a heat absorption exceeding 1800 to 2400 
B.T.U. per square foot per hour. As each square foot of 
steam radiating surface requires about 250 B.T.U. per hour 
for steam, and 150 B.T.U. for hot water, one square foot of 
heating surface would imder these conditions supply from 7.2 
to 9.6 square feet of radiating surface for steam and 12 to 16 
square feet for hot-water heating. 

If we consider that one pound of coal will in its combustion 
give 8,000 to 10,000 heat-units to the steam or water, and that 
if we bum on one square foot of grate 4 pounds of coal per 
hour we shall have from 32,000 to 40,000 B.T.U. per hour. 
We find this on the basis stated above would supply from 115 
to 140 square feet of steam radiating surface per hour, and 
about two-thirds more of hot water. It is ex-ident that if twice 
as much coal be burned j)er square foot of grate, that t\i'ice as 
much radiating surface could be supplied with steam; increas- 
ing the rate of cumbustion would produce, however, a large 
chimney waste and a loss in efficiency of the boiler unless there 
was a corresponding increase in heating surface; for this reason 
• the lower rate of combustion is usually preferable. 

The table on page 193 gives an abstract of the results of 
tests of two house-heating boilers made by the author under 
the usual conditions of operation. 

The ratio of grate surface to radiating surface gives a fair 
check when comparing two or more boilers for the same install- 
ation, but the amount of heating surface does not, as the heating 
surfaces of cast-iron boilers and heaters vary greatly in their 
efficiency. Too much heating surface may be as undesirable 
as too little due to excessive cooling of the furnace gases. 



STEAM-HEATING BOILERS— HOT-WATER HEATERS. 193 



TESTS OF HOUSE-HEATING BOILERS. 



Kind of Boiler. 



Area of grate, square feet 

Water-heating surface, square feet 

Steam-gauge pressure, pounds 

Temperature of air, degrees Fahr 

Temf>erature of feed-water, degrees Fahr 

Dry coal consumed per hour, pounds 

Total ashes and refuse per hour, pounds 

Dry coal f>er square foot of grate per hour, pounds . . 

Quality of steam, per cent 

Total weight of water evaporated per hour, pounds. . 

Actual evaporation per pound of fuel 

Actual evaporation per |)Ound of combustible 

Equivalent evaporation f>er pound of combustible 

from and at 212° Fahr 

Efficiency, per cent (about) 



Wrought-iron 


Cast-iron 


Water-tube. 


Sectional. 


2.28 


3.21 


100.06 


41.17 


7-35 


$ ^\ 


35 


89 


40 


83 


12.26 


17 3 


2.89 


3-2 


5 98 


5-4 


98.2 


97 


316 


13s 


6.82 


7.8 


8.40 


. 96 


10 


10.6 


69 


75 



The example considered on the preceding page would give 
160 sq. ft. of radiating surface to one sq. ft. of grate surface 
for steam, and 280 for hot water, for burning 4 pounds of coal 
per hour on one square foot of grate surface. 

75. Water Surface — Steam and Water Space. — The surface 
on the water-line from which ebullition takes place should 
be so large that the velocity of steam will not be great enough 
to project particles of water into the main steam-pipes. Prac- 
tice is variable in this respect; in successful plants it will be 
found that from one-third to one square foot of surface is pro- 
vided per horse-power or per 100 square feet of radiating surface. 
The greater this surface the less water will be carried out of 
the boiler with the steam, other things being equal. 

There is much variation in the amount of water and steam 
space provided in various kinds of boilers: in the fire-tube and 
shell boilers there is much more space than in water-tube and 
sectional boilers. A large amount of water and steam absorb 
the heat slowly, but on the other hand they require less fre- 
quent attention and are more regular in operation. The fol- 
lowing rules hav^ been given : 

Tredgold * states that the volume of steam space should 

* Thurston's Steam-boilers. 



194 HEATING AND VENTILATING. 

be sufficient to prevent variations in pressure exceeding i in 
30, by irregular use. 

In the ordinary tubular boilers to-day there will be found 
about 2.0 cubic feet of water and i.o cubic foot of steam per 
horse-power, and about one-third the above amounts for the 
water-tube boilers. 

76. Requisites of a Perfect Steam-boiler. — ^The late Mr. 
George H. Babcock of Plainfield, N. J., gave as the results 
of his experience the following requisites for a perfect steam- 
boiler for power purposes: 

I St. The best materials sanctioned by use, simple in con- 
struction, perfect in workmanship, durable in use, and not 
liable to require early repairs. 

2d. A mud-drum to receive all impurities deposited from 
the water in a place removed from the action of the fire. 

3d. A steam and water capacity sufficient to prevent any 
fluctuation in pressure or water-level. 

4th. A large water surface for the disengagement of the 
steam from the water in order to prevent foaming. 

5th. A constant and thorough circulation of water through- 
out the boiler, so as to maintain all parts at one temperature. 

6th. The water space diNided into sections, so arranged 
that should any section give out, no general explosion can 
occur, and the destructive effects will be confined to the simple 
escape of the contents; with large and free passages between 
the different sections to equalize the water Une and pressure 
in all. 

7th. A great excess of strength over any legitimate strain; 
so constructed as not to be liable to be strained by unequal 
expansion, and, if possible, no joints exposed to the direct 
action of the fire. 

8th. A combustion-chamber, so arranged that the combus- 
tion of gases commenced in the furnace may be completed be- 
fore they escape to the chimney. 

9th. The heating surface as nearly as possible at right 
angles to the currents of heated gases, so as to break up the 
currents and extract the entire available heat therefrom. 



STEAM-HEATING BOILERS— HOT- WATER HEATERS. 195 

loth. All parts readily accessible for cleaning and repairs. 
This is a point of the greatest importance as regards safety 
and economy. 

nth. Proportioned for the work to be done, and capable 
of working to its full rated capacity with the highest economy. 

1 2th. The very best gauges, safety-valves, and other fix- 
tures. 

The same requirements apply equally well to a boiler for 
heating, but the relative importance of the various require- 
ments might be different, and some might be omitted as imim- 
portant; thus, for instance, the mud-drum, which is of import- 
ance in a boiler for power, because it is receiving constant 
accessions of water with more or less impurities, is seldom 
on heating boilers when they are supplied with water of con- 
densation. The importance of provisions for cleaning is less 
in heating than in power boilers, but should not be neglected. 

77. General Types of Boilers. — Pawer-boUers. — It seems 
necessary to consider boilers built for high-pressure steam and 
of large sizes as a separate class from those used principally in 
heating small buildings, although boilei:s of similar structure 
may be constructed for heating. These boilers will be spoken 
of as power-boilers, and are required to fulfill conditions as to 
strength and capacity not needed in heating-boilers. 

The principal boilers of this type now in use can be grouped 
into two classes, viz., fire-tube and water-tube boilers, and one 
or the other of this type must be used for heating purposes, 
with the present condition of the market, whenever high-pres- 
sure steam is required. 

The fire-tube or common tubular boiler consists of a cylin- 
drical boiler with plain heads, connected by a large number of 
tubes which serve as passages for the smoke or heated gases. 
The fire is built underneath, and the smoke passes horizontally 
either twice or thrice the length of the boiler. The general 
form of this boiler is shown in Fig. 135. This boiler is also 
used sometimes in a vertical position with the fire beneath one 
head, in which case it is called a vertical tubular. The water- 
tube boilers have the water in small tubes, and the heated 



196 IIEATISU AND VENTILATING. 

gases pass out between the tubes. In this class of boilers 
the steam is contained in drums or horizontal cylinders, which 
are located above the heating surface. The tubular boilers 
are made in small sizes, lo horse-power and larger, while the 
water-tube boiler for power is seldom less than 60 horse-power 
capacity, 

Ilealing-hoiUrs. — The boilers which are used for steam 
heating are designed in a multiplicity of forms, and present 
examples of nearly everj- possible method of producing extended 
surfaces, both of the water-tube and fire-tube tjpes. They 
are generally built for low-pressure steam, and are expected to 
be used mainly in buildings where the condensed water is 




Fic. 135. — Jloriiontat Tubular Boiler. J 

returned by gravity lo the boiler without pumps or traps. Thejr^ 
are usually built in small sizes having a capacity of 250 to 2000 
ft. of radiating surface (2I to 20 H.P.), and are fitted with 
safety-valves, water and steam gauges and damper regulators. 

The limits of this book prevent a detailed description of 
any make of heating-boiler, but the leading general types are 
described. Several t^pes of the power-boiler are described 
quite in detail, and much that is said with respect to them 
will apply in a general way to heating- boilers. 

The following classification of steam -heating boilers was 
suggested by one presented by Mr. A. C, Walworth in a paper 
before the New York Convention of Master Steam and Hot- 
water Fitters, June, 1S94; 




STEAM-HEATING BOILERS— HOT-WATER HEATERS. 197 



CLASSIFICATION OF HEATING-BOILERS. 



Plain 
Surface 



Spherical 

^ 1. J • I ^ Vertical 
Cylindrical ^ jj^rizontal 



Extended | ^^^^^^^^ ^^^^> ProjecUng Tubes 
Surface 



Boiler 



Divided 
Surface 



Cast Iron, Irregular Surface 
Fire-tube 



Tubular 



Vertical 

Horizontal 

Locomotive 



Water-tube 



Straight tubes 
Curved '' 
Spiral 
Coil of 
Drop 



I ( 



Sectional < 



Horizon Uxl 



Vertical 



Packed joints 
Screwed * ' 
Faced 

Packed joints 
Screwed * * 
Faced ** 



78. The Horizontal Tubular Boiler. — This boiler is manu- 
factured in many places, so that in many respects it is a stand- 
ard article of commerce, and it can be purchased in nearly 
every market for a slight advance over the cost of materials 
and labor used in its construction. In the construction of this 
boiler the shell is now almost invariably made of soft steel of 
a thickness depending upon the pressure which the boiler is 
expected to sustain. The heads of the boiler are made of flange 
steel, and are generally ^ inch thicker than the material in the 
shell. Lap-welded steel tubes are almost fnvariably used, the 
standard sizes are based on outer diameters. The tubes are 
expanded into the heads of the boiler and may or may not be 
beaded, and are generally arranged in parallel vertical rows 
in the lower two- thirds part of the boiler. In some instances 
the middle row of tubes is omitted with good results. It is 
not a good plan to stagger the tubes, since in that case they are 
difficult to clean, and also act to impede the circulation of the 
water. The boiler should be provided with manholes, with 



108 



HEATING AND VENTILATING. 



strongly reinforced edges, so that a person can enter for clean- 
ing. The heads of the boiler above the tubes should be thor- 
oughly braced in order to sustain safely any pressure from the 
inade of the boiler. 

Domes are often placed above the horizontal part of the 
boiler, and serve to increase the capacity for the storage of 
steam and also provide ready means of drawing off dry steam. 
The dome is always an element of weakness, and if used it 
should be stayed and reinforced in the strongest possible man- 
ner. The dome is frequently omitted, and steam taken directly 
from the top of the shell or drawn through a long pipe with 
numerous perforations, termed a petticoat pipe. 

In construction this boiler must be strongly braced wher- 
ever any flat surfaces are exposed to pressure, and the girth 
and longitudinal seams must be riveted in such a maimer as 
to secure the maximum strength. 

The following table gives principal dimenMons for a series 
of horizontal tubular boilers designed for a working pressure 
of 80 to 100 pounds per square inch: 





.«>o 


OOD 


i6dd 






3000 


4000 


Sooo 


6000 


aooo 














■0 


11 


It. 


.0 


>s 


30 


4« 


50 


00 


so 








Diuneter of bdUcr iachu 

Lewnb o[ boiler. [»t 

Thickuu of id»U. locbu.. . . . 
Thiekntw of beidi. lnch«. . . . 


1/16 

6 


Ti 

'/A 

S/16 

Jl 


3fl 
8 

J/ift 
g 

JO 


36 

3/t 


■>/3> 

IBs 

4000 


461 
46W 


9/31 

3/8 

S60( 


11 

'i 

76; 


S/.6 
SO( 


I/J 
16 
83 


66 


Number of duel 

Di»ni«wr ol Bm», tnchem. . , 

Sqnan feel of bo«tiog lutface 

Proper diltn. of stnoke-pipc 

(ao' chimnti') inches- 

Wt. of grUoandS.lurei, lb... 


USOO 

JSOO 



Fifteen iquare fe 



a each hone-po'm- 



79. Locomotive and Marine Boilers.— Boilers of the horizon- 
tal tubular type with a fire-box entirely enclosed and surrounded 
by heating surface are usually termed locomotive boilers from 
the fact that such construction is common on locomotives. 
Boilers of this style are sometimes used for stationary power 
purposes, and posses the advantage over the plain tubular 



STEAM-HEATING BOILERS— HOT- WATER HEATERS. 199 

boiler of reqiiiring no brick setting. They are not, however, 
as strong in form as the plain tubular, since large flat surfaces 
have to be used over the lire-box. 




Marine Boilcrs.—h cylindrical boiler with an internal cylin- 
drical fire-box is principally used on large boats. The fire-box 
is often corrugated. This form of boiler 
is very strong and efficient, but be- 
cause of cost of construction has been 
little used for stationarj- purposes. 

Vertical Boilers.— Vertical boilers of 
large size are made in every respect 
like the horizontal tubular boiler, but 
are set so that the flame plays directly 
on one head and the heated gases pass 
up through tubes. These boilers are 
generally provided with a water-leg 
which extends below the lower crown 
sheet and is intended to recei^-e deposits 
of mud, etc., from the boiler. They are 
usually made so that the heat passes 
directly out of the top of the flue,, but in 
some cases the heat is made to pass 
down a portion of the length of the ex- ' '^^" jj^i^r. 
temal shell before being discharged. 

They are economical in the use of fuel and occupy very small 
amount of floor-space; they require, however, a great deal 




200 



HEATING AND VENTILATING. 



of head-room, are very easily choked up with deposits and sedi- 
ment, very difficult to clean, and very likely to leak around 
the tubes in the lower crown-sheet, and consequently have a 
short life. 




Fig 138 — Babcock & W Icoi Boflec 

Vertical boilers with horizontal radial tubes projecting 
outward with ends closed, known as porcupine boilers, and 
vertical boilers of the water-tube tj-pe are on the market. 

80. Water-tube Boilers.— The water-tube boilers, which 
are used for power purposes, are designed to withstand great 




pressurt's. and can be purchased in sizes ranginii; from 60 to 500 
horse-power per boiler. The general con;=tritetion of these 
boilers is such as to have Ihe water on the inside of the tubes, 
and the fire without. There are two <;eneral forms: first. 
those with straJL'ht tubes, and second, those with cnrwd tubes. 



STEAM-HEATING BOILERS— HOT- WATER HEATERS. 201 

In all cases they have large steam-drums at the top, which 
are connected to the heating surface by headers filled with water. 
In the'Babcock & Wilcox, Heine, and Root boilers the tubes are 
inclined and parallel, and are connected at the end with headers, 
the fire being applied in each case under the elevated portion of 
the inclined tube, so as to insure circulation uniformly in one 
direction. 

In the Babcock & Wilcox boiler, forged zigzag headers 
are used; Jn the Root boiler, the tubes are connected together 




Fig. i4o.~Stirling Boiler. 



by external U-shaped bends; in the Heine boiler (Fig. 141), 
the tubes are connected to large, flat-stayed surfaces. In the 
Babcock & Wilcox and Heine boilers, feed-water is supplied at 
the lower part of the top drums; while in the Root boiler, it is 
supplied to a special drum in the down-circulation tubes at 
the back end of the boiler. The StirHng boiler has three hori- 
zontal drums at the top connected by curved tubes to a single 
lower drum at the back end of the boiler; the Hogan has one 
drum at top and two at bottom, which are parallel and con- 
nected by curved tubes, and also a series of down-circulating 



202 



HEATING AND VENTILATING. 



tubes connecting the same drums, but not exposed to the heat 
of the fire. In the Stirling boiler, the feed-water is introduced 
in the top drums; in the Hogan boiler, into a special heater 
and purifier arranged as a part of the downward circulation. 

The Harrison boiler consists of an aggregation of spheres 
of cast iron or steel connected by necks, forming what is to be 
considered rather as a sectional than a water-tube boiler. 
These spheres are held in place by bolts, which will stretch 
and act as safety-valves in case of excessive pressure. 

In addition to the water-tube boilers for power purposes 
which have been mentioned here, there are many others which 
cannot be described in the space at our conmiand, but of which 




Fig. 141. — Heine Boiler. 



we may name the National, Campbell & Zell, and the Caldwell 
as worthy of notice. 

All the water-tube boilers are provided with mud-drums, 
which are frequently cylinders removed from the circulation 
and intended to receive any deposits of scale or material which 
is loosened in the process of circulation. 

81. Hot-water Heaters. — Hot-water heaters differ essen- 
tially from steam-boilers, principally in the omission of a reser- 
voir or space for steam above the heating surface. The steam- 
boiler might answer as a heater for hot water, but the large 
capacity left for the steam would tend to make its operation 
slow and quite unsatisfactory. 

The passages in a hot-water heater need not extend so 
directly from bottom to top as in a steam-heater, since the 



BTEAH-HEATINQ BOILERS— HOT-WATER HKATER8. 203 



problem of providing for the early liberation of the steam- 
bubbles does not have to be considered. In general, the heat 
from' the furnace should strike the surfaces in such a manner 
as to increase the natural circulation, and not act to produce 
a backward circulation. This may be accomplished in a certain 
measure by arranging the heating surface so that a large pro- 
portion of the direct heat will be absorbed near the top of the 
heater. 

There is a great difference of opinion as to the relative 
merits of horizontal and vertical heating surfaces for this pur- 
pose, but the writer cannot find 
that any experiments have been 
made which satisfactorily decide 
this question. Where the surface 
is very much divided, and the fire 
is maintained at a high tempera- 
ture, considerable steam is likely 
to be formed, and this always 
acts in a certain measure to in- 
crease circulation in the circulat- 
ing-pipes and in the heater; it is 
likely also to produce a disagree- 
able crackhng noise. 

Practically, the boilers for low- 
pressure steam and for hot water 
differ from each other very httle 
as to the character of the heating surface, and in describing 
the general classes which are in use no attempt will be made to 
make any distinction as to whether the apparatus will be used 
for hot -water or steam heating. If designed for steam heating, 
a reservoir or chamber connected with the circulating system 
is in e\ery case provided, containing water in its lower part 
and considerable steam capacity above the water-line, also 
sufficient area of water-surface to permit the separation of 
the steam from the water without noise and violent ebullition. 

82. Classes of Heating-boilers and Hot-water Heaters. — 
Flain-surface Boilers. — There are probably no boilers or heaters 




2M 



HEATING AND VENTILATING. 



built at the present time with a plain surface, either spherical 
or cylindrical, since the expense of a gived amount of surface 
in that form would practically preclude its use. 

Exlended-surjace Beaters {Figs. 143 and 144).— Heaters of 




this class with extended and irregular surface, are used quite 
extensively in hot-water heating, and with the addition of 
domes are used to some extent in steam-heating. In these 
heaters the water is received at the lowest point, as at --1. and 
is heated as it gradually rises, receiving the effect of the fire 
at various projections, and is finally discharged at B. The 



STEAM-HEATING BOILERS— HOT-WATER HEATERS. 205 

grate is at G, the smoke being discharged at 5. The smoke 
and heated gases move in nearly a direct line in Fig. 143, and 
in a sinuous course in Fig. 144. 

A form which is in extensive use, and in which water and 
smoke are each grouped in one body, is shown in Fig. 145. 
In this case the extended surface is produced by the wedge- 
shaped hollow prisms extending over the fire-space. The 
heated gases have a return circulation around the lower portion 
of the heater, and also come in contact with a top dome from 
which the heated water is drawn off. 

Heaters belonging to the extended-surface class made with 
vertical cylinders, into which are connected either straight 
horizontal tubes with closed end, as shown on the right-hand 
side of Fig. 146, or U-shaped projections of pipe either hori- 
zontal or slightly inclined, are in use for both water- and steam- 
heating. In case they are used for steam-heating the water- 
line is carried at sufficient distance from the top of the cylinder 
to give the required steam-space, and the heater is supplied 
with both pressure- and water-gauges. The heated gases pass 
around the cylindrical part of the boiler and may be made 
to circulate among the projections by means of baffle-plates. 

Tubular Boilers. — Heating-boilers with fire-tubes and with 
a steel shell similar in construction to Fig. 135 for both hori- 
zontal and vertical tubular boilers are in use for heating to con- 
siderable extent in the forms already described. Modifications 
of these, with return flues arranged so that the heat passes 
both upward and downward, and also with two or more short 
cylindrical shells connected together by tubes filled with water, 
are in extensive use. Very few horizontal tubular boilers, or 
boilers of the locomotive type, are used for the heating of small 
buildings. 

Water-tube Boilers. — Water-tube boilers of all classes and 
various modifications are in extensive use for heating. The 
tubes are made of either cast-iron or wrought-iron pipe. The 
pipe-boilers which are in the market are arranged with nearly 
every form of heating surface; some are built with heating 
surface in the form of the pipe-coil and others in the form of 



20S H£ATING AND VENTILATING. 

a manifold coi]. Still other boilers have the pipb arranged in 
the form of a spiral connecting with a receiving-drum below 
and a steam-drum above. The heated gases are arranged to 
move in some cases parallel with the surfaces, and in other 
cases at right angles. 

The Field tube is used entenavely for the purpose of increas- 
ing the heating surface; in its original form it consisted of a 
tube with a closed end projecting downward and expanded 
into the boiler-shell; into this extended another tube which 
did not reach quite to the bottom, and was held in position by 
an internal perforated support, as shown in Fig. 147. This is 




used in heabng boilers with various modifications both pro- 
jecting downward and horizontally When used projecting 
downward, it is termed a drop tube and is supplied either with 
an internal tube as shown or a partition; when used hori- 
zontally the internal tube is frequently supplied from a com- 
partment separated from that to which the external tube is 
attached. Fig. 148 illustrates a type of heating-boiler which 
is quite extensively used for both hot water and steam, and is 
built by different manufacturers, either of steel or cast iron. 
The heater consists of a cylindrical drum, the lower surface of 
vbich is covered with tubes of the type described which pro- 
ject downward. The tubes directly over the fire and over the 
fire door are short, while those around the fire are sufficiently 



STEAM-HEATINa B0II-ER8— HOT-WATER HEATERS. 207 

long to form the extenial walls of the heater. The return 
water is received in one of the long pipes near the bottom of 
the heater, and the steam or heated water is taken off at the 
top. The drum in one of these heaters is provided with a 
baffle-plate connected to the diaphragm in the drop-tube, so 
that the circulation must take place in a vertical direction in 
the tube. 

Fig. 149 shows a heater in which the surface is made up 
partly of pipe-coils and partly of drop-tubes. The return 
water is received in a drum surrounding the grate, and as it 
is warmed passes to the top drum of the heater, from which it 




Fig. 148.— Drop-tube Surface. Fig. 145. — Drop-tube and Coil-heater. 



flows to the building; a type of heater in many respects similar 
is made without drop-tubes, the whole surface being obtained 
by use of pipe-coils, made either with return bends or with 
branch tees. 

Sectional Boilers. — The greater number of cast-iron boilers 
are made by joining either horizontal or vertical sections. 
These sections are joined in some instances by a screwed nipple, 
in other cases by a packed or faced joint, and are held in place 
with bolts. The sections generally contain water and steam, 
and the heated gases circulate around the sections in flues 
provided for that purpose. The joints in the flues are usually 
made tight enough to prevent the escape of smoke by the use 



208 HEATING AND VENTILATING. 

of an asbestos cement or a stove putty. This type of boiler 
has been largely adopted on account of the ease with which 
they can be shipped and delivered into the cellars of buildings; 
also on account of their lower cost due to the combining of three 
or four different castings to make up a full line of boiler sizes. 
Horizontal Sections. — Fig. 150 represents a type of heater 
in which the various sections are horizontal, the surface being 



jiUix, 




Oo 1 






Oo 
Oo 




Fio, 150. Fig. 151 

Boiler with Horizontal Boiler with Horizontal Sections. 

Sections. 

increased to any amount by adding sections. This form is used 
extensively in a number of hot-water heaters. Fig. 151 shows 
another form of boiler made in a similar manner, but with the 
sections of such form as to produce both an up and down cir- 
culation within the heater. The up circulation takes place 
over the hottest portion of the fire, the down circulation in 
special external passages which are not heated. 

Vertka! Sections. — Boilers with vertical sections are made in 
the same manner in many respects, the sections being united 
by internal or external connections. When united by external 



STEAM-HEATING BOILERS— HOT-WATEE HEATERS. 209 



connections, screwed nipples connecting the sections to outside 
drums, of the general form as shown in Fig. 153, are usually 
employed. In this case the return-water is received into hori- 
zontal drums, AA, which extend the fuU length of the heater, 
and Sows into the lower part of each section. The steam 
or hot water is drawn off from a similar drum, B, which extends 
over the top of the beater and is connected with each section 
by a screwed nipple. Fig. 152 shows methods of attaching 
steam- and water-gauges. This form is used quite extensively 
in steam-heating and to some extent tor 
hot-water heating. 

83. Heating-boilers with Magazines. 
— Many of the heating-boilers are 
manufactured as required with or 
without a magazine to hold a supply 
of coal. The magazine in most cases 
consists of a cylindrical tube opening 
at or near the top of the heater and 
ending eight to twelve inches above the 
grate. The magazine is filled with 
coal, which descends as combustion 
takes ["place at the lower end, and 
provides fuel for further combustion 
(see Fig. 142). The magazine works 
successfully with anthracite coal, which 
is that ordinarily employed in domestic 
heating, but it takes up useful space in the heater, decreases 
the effective heating surface for a given size, and in that 
respect is objectionable. The writer's own experience would 
lead him to believe that the magazine heater, except in very 
small sizes, requires as much attention as the surface burner, 
and consequently has no special advantage.* 

84. Heating-boilers for Soft Coal. — It is quite probable 
that no furnace, either for power- or heating-boilers, has yet 

* Magazine heaters have been constructed with a magazine set obliquely 
above and to the side of the grate, and in that position are not open to all the 
objections stated. 




Fic. rs*. 



210 HEATING AND VENTILATING. 

been produced which will consume soft coal without more or 
less black smoke. This smoke is due principally to the imper- 
fect combustion of the hydrocarbons contained in the coal. 
The hydrogen burning out after the gases have left the fire 
leaves solid carbon in the form of small particles, which float 
with and discolors the products of combustion. The amount 
of loss as found by experiment in Sibley College, even when 
dense black smoke is produced, seldom reaches one per cent, 
and is of no economical importance. The sooty matter pro- 
duced in the combustion of this coal is likely to adhere to the 
water-heating surfaces, and if these are minutely divided it 
will be certain to choke the passages for the gases of combus- 
tion. For the combustion of soft coal those heaters have been 
the most successful which have a grate with small openings, 
and with an area 50 to 70 per cent as large as that needed for 
anthracite coal, also with the heating -surface of comparatively 
simple form and arranged so as to be easily cleaned. It is 
considered important that the air-flues be so arranged as to 
keep the products of combustion as hot as possible. This coal 
is likely to swell when first heated, and cannot be fed success- 
fully by a magazine. 

85. Boilers in Batteries. — ^Two or more boilers or heaters 
are sometimes used as a battery for heating on account of 
limited headroom, insurance against breakdown, etc. A single 
unit will generally give a higher efficiency on the coal burned, 
due mostly to more efficient combustion of the coal and the 
smaller amount of heat wasted in heating the gases going up 
the chimney. If two units are used they should be installed 
with separate dampers which can be closed off tight, preventing 
the leakage of air into the chimney through the unused unit. 



STEAM-HEATING BOILERS— HOT-WATEB HEATERS. 209 

connections, screwed nipples connecting the sections to outside 
drums, of the general form as shown in Fig. 152, are usually 
employed. In this case the return-water is received into hori- 
zontal drums, AA, which extend the full length of the heater, 
and Sows into the lower part of each section. The steam 
or hot water is drawn off from a similar drum, B, which extends 
over the top of the heater and is connected with each section 
by a screwed nipple. Fig. 152 shows methods of attaching 
steam- and water-gauges. This form is used quite extensively 
in steam-heating and to some extent for 
hot-water heating. 

83. Heating-boilers with Magazines. 
— Many of the heating-boilers are 
manufactured as required with or 
without a magazine to hold a supply 
of coal. The magazine in most cases 
consists of a cylindrical tube opening 
at or near the top of the heater and 
ending eight to twelve inches above the 
grate. The magazine is filled with 
coal, which descends as combustion 
takes [place at the lower end, and 
provides fuel for further combustion 
(see Fig. 142). Tlie magazine works 
successfully with anthracite coal, which 
is that ordinarily employed in domestic 
heating, but it takes up useful space in the heater, decreases 
the effective heating surface for a given size, and in that 
respect is objectionable. The writer's own experience would 
lead him to believe that the magazine heater, except in very 
small sizes, requires as much attention as the surface burner, 
and consequently has no special advantage.* 

84. Heating-boilers for Soft Coal. — It is quite probable 
that no furnace, either for power- or heating-boilers, has yet 

* Magazine heaters have been constructed with a 
above and to the side of the gra^te, and in that posilioi 
objections stated. 




Fic. 151. 



212 



HEATING AND VENTILATING. 



in order that the entire bottom of the boiler may be drained 
at the blow-off pipe. One of the lugs of the boiler on each side 
should be anchored in the brickwork; the others should rest 
on rollers, which in turn rest on an iron plate embedded in the 



Cfe^ 




brick walls. This permits expansion due to heating and cooling 
to take place without straining the boiler. If the boiler is 
not over 14 feet in length, two lugs on a side will be sufficient 
to sustain it, but if it is of greater length, more lugs will need 
to be suppUed. This brickwork surrounding the boiler is 



SETTINGS AND APPLIANCES. 



213 



more durable if built with an air-space, as shown in Fig. 155. 
It must be thoroughly stayed, by means of iron braces, con- 
nected with tie-rods of wrought iron at top and bottom to 
prevent transverse or longitudinal motion. The top may be 
arched over so as to leave a passage for the hot gases directly 
over the shell, as in Fig. 153, or made to rest directly on the 
boiler, and the hot gases taken away at the front end by means 
of a flue, usually termed a breeching, which extends to the 
chimney. The practice of taking the heated gases from the front 




Fig. 155. — Sectional View of Boiler-setting. 



end of the boiler is rather more common than that of returning 
them to the back end over the top, and there are many engi- 
neers who believe that the hot gases injure the boiler when 
coming in contact with the shell above the water-line. Figs. 
'54f 155, and 156 show longitudinal and transverse sections 
of a boiler-setting, with smoke-pipe or breeching in front, which 
can be highly commended as representing the best practice. 

The depth of foundation to be used in boiler-setting will 
depend ujwn the character of the soil and the weight of the 
boiler. For large tubular and water-tube boilers it should 



214 



HEATING AND \'ENTILATING. 



generally be not less than 3 feet. Fire-brick of the best quality 
sbould be used to lioe the brick walls where exposed to the fire 
from the grate to the water-line of the boiler, and these should 
be airanged so that if necessary they can be renewed without 




disturbing the outer brickwork. In the setting jhow-n in Figs. 
154-155 the top of the boiler is covered with a coaling of some 
good, non-conducting material, for which magnesia and asbestos 
may be recommended, put on while in a plastic condition to the 



SETTINGS AND APPLIANCES. 



215 



depth of 2 inches. Mineral wool is also used for this purpose. 
Brickwork is often used; but it is heavier, and quite liable to 
crack from the effects of heat. 

87. Setting of Heating-boilers. — If heaUng-boilers are to 
be set in brickwork, the special directions which have already 
been given can be applied, with such modifications as may be 
needed for the boiler in question. Nearly all heating-boilers 
are now set in what is called a portable setting, in which no 
brick whatever b used. Some of the heaters are constructed 
in such a manner that no outside casing is required, as in Fig. 
159; others require thin casing of galvanized or black iron which 
is lined with some non-con- 
ducting material, as magne»a, 
asbestos fibre, or rock wool, 
which is placed outside the 
heater and arranged so as -to 
enclose a dead-air space, as in 
Fig, 158. These coverings are 
nearly as efficient in prevent- 
ing the loss of heat as brick- 
work, and they form a more 
cleanly and neater appearing 
job. 

•The slight amount of heat 
which escapes from such a set- 
ting is seldom more than that required to warm up the base- 
ment or room in which the heater is located. 

The boiler must in all cases be provided with a steam- 
gauge, safety-valve, and damper regulator, all of which are 
specially described later. The steam-gauge should be either 
connected below the water-level or else provided with a siphon 
to prevent dry steam entering the interior tube. A safety- 
valve of the single-weighted type is preferable and should 
be connected at the top of the heater. Fig. 158 represents 
a boiler with portable setting with external iron casing and 
equipped with all appliances, and Fig. 159 represents a portable 
setting without enclosing case. 




Fic. 1 5;.^ Brick- set Magazine Boiler. 



216 



HEATING AND VENTILATING. 



Hot-water heaters are set in the same general manner as 
steam-boilers. Each should be provided with thermometers 
showing both the tanperature of the flow and the return water, 
and with a pressure-gauge graduated to show pressure of water 
in feet and sufficiently large to show any variation in height in 
the open expansion tank. The dampers to a hot-water heater 
cannot be opened and closed by variation in pressure, but 
reliable thermostats are now on the market which will operate 




Fig. 158— Healing-boiler 
Portable Setting. 



Fig. isq. — Heating-boiler with 
Portable Setting. 



the dampers by change of temperature in the various rooms 
of the building. 

88. The Safety-valve. — The safety-valve has been used 
since the earliest days of boiler construction for reducing the 
pressure when it reached or exceeded a certain limit. It has 
been built in various forms, but in every case has consisted 
essentially of a valve opening outward and held in place by a 
weight or a spring. One form in common use consists of a 
valve held in place by a weight on the end of a lever, shown 
in Fig. 160. In this form of safety-valve the force required to 



SETTINGS AND APPLIANCES. 



217 



lift the valve can be regulated by sliding the weight to different 
positions on the lever. The form shown in Fig. i6i eonsists 
of a single weight suspended from the valve and hanging in 
the upper part of the 
boiler. This form is to 
be commended, since it 
cannot be adjusted with- 
out opening the boiler. 

A form used very 
extenavely for low-pres- 
sure heating-boilers con- 
sists of a single weight 
resting on a valve, as 

shown in Fig. i6a; its principle of operation is the s 
that of the other valves, 
and frequently called, 
it opens, a pop-valve. 



Fio. 160. — Lever Safety-valve, Modem Fonn. 



A form much used on power- boilers, 
from the suddenness with which 
consists of a very quick -opening 
valve held in place with a spring, 
one form of which is shown in Fig. 
163. 

It is desirable that the safety-valve 
be made in such a marmer that the 
engineer or attendant to the boiler 
cannot manipulate it at pleasure so 
as to maintain a higher pressure 00 
the boiler than prescribed. 

Serious accidents have been caused 
by excessive weighting of the safety- 
valve through ignorance or careless- 
ness on the part of the attendants, 
and for this reason a class of valves 
should be selected which cannot be 
tampered with. Some of the safety-valves are provided with 
an external case which can be locked, and others are provided 
with internal weights, as already described. The lever safety- 
valve offers the greatest temptation for extra weighting and 
should rarely be used. 




i 



218 



HEATING AND VENTILATING. 



Safety-valves should be fastened directly to the boiler with- 
out any intervening valves or piping. 

88. Safety-valve Area. — TMs must be sufficiently large to 
reduce the boiler pressure effectually when the valve is open 
and when a brisk fire is burning on the grate. It may be com- 
puted from the following considerations: 

The steam which will flow through one square inch of open- 
ing in one hour of time was found by Napier to equal in 
pounds nearly 50 times the absolute pressure of the steam; 
further, it has been found by experiment that the safety-valves 
in ordinary use open only to such an extent as to make I of 





Fig. 163. — Section of Spring or 
Pop Safely- valve. 

the total area of the valve effective in reducing the pressure. 
From these considerations it will be seen that the area of the 
safety-valve in inches should be ^b the weight of steam gener- 
ated per hour, divided by the absolute pressure. Considering 
that 100 lbs, of steam can be generated from each square foot 
of grate per hour, this would be equivalent to the following rule: 
The area in square inches is equal to 18 times the grate surface 
in square feet, divided by the absolute pressure. 

The following table gives the areas of grate surlaces, in 
square feet, for direct spring-loaded safety-valves, required 
by the Massachusetts Board of Boiler Rules: 



SETTINGS AND APPLIANCES. 







W_-I^ 


H'--i22. 


If— 1?2. 


w-i^ 


w-^^ 


w--^ 






36(« 


3600 


3600 


3600 


3600 


J600 








P- 6s 




p- 140 


P- IdO 


p- 240 






yl-.401 


4-329 


A-.M7 


A-.HA 


4 -.224 


4 -,213 


Ma.imun 


PrtMure 


Zero to IS 


Over 25 


Over JO 


Over 100 


Over ISO 


Over 100 


allowed ptt Square 


Pound., 






to IJO 


to JOO 


Poundl. 


Inch on the Boiler. 




Pound.. 


Pound.. 


Pound.. 


Pounds. 




io laches. 






Area 


of Grate. 


n Square Feet. 




, 


.7854 


2, 00 


3. SO 


2.75 


3. as 


3,S 


3-7S 


ll 


1.J371 


3.25 


4 






3S 


S 00 


S 


S 


S.7S 


ll 


I 7671 


4,50 


s 


SO 


6 


oo 


7.^5 


8 




8-So 


I 


3.U'6 


8,00 


9 


7S 


10 


75 


13-00 


14 





15.00 


I) 


4.9087 


12,50 


IS 


00 


16 


5° 


20.00 






23.00 


3, 


7.0686 


17.7s 


31 


SO 


>4 


00 


29 00 


31 


s 


33 3S 


3i 


9,62.1 


24.00 


29 


50 


32 


SO 


39. SO 


43 




4S.3S 


4 


12.5660 


31. so 


38 


'S 


42 


SO 


5'. 50 


56 




59 00 


4) 


IS. 9040 




48 


SO 


S3 


SO 


65.00 


71 




74.35 


5 


19.63SO 


49 00 


60 




66 


00 


80,00 


S8 


* 


93.35 



When the conditions exceed those on which the table is 
based, the following formula shall be used: 

A = area of direct spring-loaded safety-valve in square 

inches per square foot of grate surface. 
1^ = weight of water in pounds evaporated per square foot 

of grate surface per second. 
P=pres^re (absolute) at which the safety valve is set to 

blow. 
A table of areas of grate surfaces, in square feet, for other 
than direct spring-loaded safety-valves, will be found on p. 220. 
Various rules quite different from those in the tables are 
given in treatises on boiler construction, but it is believed 
these two tables represent the best practice of to-day 
1 form a safe guide for estimating the size of safety-valves. 
riHy-valves are liable to stick fast to the seat, through 
in which case they fail to raise with excess of pres- 
et reason they should be periodically lifted from 
od otherwise inspected. 



220 



HEATING AND VENTILATING. 



Maximum Pressure Allowed per 
Square Inch on the Boiler. 


Zero to 
25 Pounds. 


Over as to 
50 Pounds. 


Over so to 
too Pounds. 


Diameter of 
iValve. in Inches. 


Area of Valve, in 
Square Inches. 


Area of Grate, in Square Feet. 


I 

>i 

2 
2| 

3 
3* 

4 

4l 

5 


•7854 
1.2272 

I. 7671 
3.1416 

4.9087 

7.0686 

9.6211 

I 2 . 5660 

15.9040 

19.6350 


I SO 
2.25 
3 00 
S SO 
8.25 

" 7S 
16.00 

21 .00 

26.7s 
32.7s 


1-75 
2.50 

3-7S 
6.50 

10.00 
14 25 
19 SO 
25 SO 
32.50 
40.00 


2.00 
3 00 
4.00 
725 
II .00 
16.00 

21. 7S 
28.25 

36.00 

44 00 

1 



r^^'n 



In case the area of the valve required is greater than 4 inches 

in diameter, two or more safety-valves should 
be provided. 

89. Appliances for showing Level of Water 
in the Boiler. — In the first boilers constructed 
floats were used, and such appliances are still 
common on European boilers. In this country 
water-gauge glasses and try-cocks are now used, 
to the exclusion of all other devices. The 
water-gauge (see Fig. 164), consists of two 
angle- valves, one of which is screwed into the 
boiler above the water-line; the other is screwed 
about an equal distance below, and these are 
connected by means of a glass tube usually | 
to I inch external diameter and strong enough 
to withstand the steam-pressure. WTien both 
angle-valves are open the water will stand in 
the gauge-glass the same height as in the 
boiler, but if either valve is closed the water- 
level shown in the glass will not accord with 
that in the boiler. Three tr>'-cocks are usually 
put on a boiler in addition to the water-gauge. 
The trj^-cocks are made in various forms, one kind being 
shown in Fig. 165, and are located so that one is above, 




Fig. 164. 
Water Gauge. 



SETTINGS AND APPLIANCES. 



221 



rthe other below, and the third at about the mean position 
I of the water-line. When the top one is opened, it should 
f show steam; when the bottom one is opened, it should show 




'5.— Try-cock. 



I water. Both try-cocks and gauge-glasses should usually be 
' put on boilers, so that the reading as shown in the water-gauge 
glass can be checked from time to time. This is necessary, 
because if dirt should get in the angle-valves or passages 
leading to the gauge-glass the determination would be 
inaccurate. 

Water-columns attached to the boiler by large pipes, both 
above and below the water-line, and fitted with try-cocks and 
water-gauge as shown in Fig. i66, are often provided. These 



I 





Pig. 166.— Wi 



I columns frequently contain floats (Fig. 167), so arranged that 
[ steam is admitted into a small whistle if the water falls below 
or rises above the required limits, and thus gives an alarm. 



HEATING AND VENTILATING. 







r Tubes. 



90. Methods of Measuring Pressure. 
— The excess of pressure above that 
of the atmosphere is measured by some 
form of manometer or pressure-gauge. 
Where the pressure is small in amount, 
a siphon, or U-shaped tube filled with 
some liquid is a very convenient means J 
of measuring pressure. 

If water, mercury, or other liquid be 
placed in the U-shaped tube it »nU be 
forced down on the side of the greater 
pressure and upward on the side of the 
less, a distance proportional to the pres- 
sure. The height of the fluid in one 
side in excess of that on the other will 
be a measure of the difference of pressure 
between that of the atmosphere and that 
in the vessel. 

Various forms of manometers axt\ 
used, of which several are shown in Fig. 168. For very! 
low pressures water is the liquid generally employed; forj 
moderate pressures up to 15 or 35 pounds mercur>' is very I 
convenient, and often used; while for high pressures a prea- 1 
sure-gauge (Fig. 169) is commonly employe 

91. The Bourdon Pres- 
sure-gauge is ordinarily used. 
This consists of a tube of 
elliptical cross-section bent 
into a circular form. The 
free end of the tube is 
attached by gearing to a 
hand which moves over a 
dial. Pressure on the inter, 
ior of the tube tends to 
straighten it, and moves 
the hand an amount pro- 
portional to the pressure. 




SETTINGS AND APPLIANCES. 



I 



Fig. 169 shows the interior of a pressure-gauge of this char- 

tacter, the dial being removed. In place of the tube a corrugated 
diaphragm is sometimes employed. A section of such a gauge 
is shown in Fig. 170. In the use of gauges of the character 
just described it is necessary to protect them from extreme 
heat. For this purpose when they are connected to a steam- 

r boiler a siphon or U-shaped form of pipe is to be used in the 
connection, so that water and not steam will be forced into 
the interior of the gauge. 

The manometers and gauges described in every case measure 
the pressure above or below 

L that of the atmosphere 

[ they measure a pressure 
lower than that of thi 
atmosphere they are com- 
monly called vacuum 
gauges, but the principle 
of construction is the same 
as described. 

The relations of various 
units used in measuring 
pressure can be readilj' de- 
termined from the follow- 
ing table of equivalents : 
1 inch of mercury = 13.58 
inches of water=i.i3i feet 
of water =0.490 lbs. per sq. 
in. =920 feet of air at 60 
degrees Fahrenheit and 
barometer pressure 30 inches. 

^9S acting on one square inch of a body. 

In any hot-water heating system it is quite important to 
.now the temperature of the water leaving the heater, and in 
many .cases also that of the return. This information, while 
not so vital to the safety of the heater as that given by a pres- 
sure-gauge on a steam-heating system, is of the same char- 

I acter, and will prove to be equally valuable in indicating 




I 



70. — Diaphragm Gauge. 

The pressures are usually taken 



224 HEATING AND VENTILATING. 

the work done by the heater, and the heat absorbed by the 
system. 

Any of the suitable forms of thermometers described in 
Chapter I can be used, but special forms in which the thermom- 
eter-bulb sets in a cup of mercury are often used, the cup being 
screwed into the pipe whose temperature is required. These 
thermometers should be set so as to extend deep into the cur- 
rent of flowing water, and there should be no opportunity for 
air to gather around the bulb; otherwise the readings will not 
be the true temperature. 

92. Damper-regulators. — Nearly all steam-boilers are pro- 
vided with an apparatus for opening or closing the dampers 
and draft-doors to the boiler as may be required to maintain 

a constant steam-pressure. For 
low-pressure steam-heating plants 
the regulator consists in nearly 
ever>' case of a rubber diaphragm 
(Fig. 171), which receives the 
steam-pressure on one side, and 
Fig. 171.— Diaphragm ^^^^ against a counter-weight 

Damper-regulator. . ^ 

resting on a plate on the oppo- 
site side. The plate is connected by a rod to a lever pivoted 
to the external case, which in turn is connected to the various 
drafts by means of chains, and so arranged that if the pres- 
sure rises the lever is lifted and' the dampers closed, while 
if the pressure falls the lever also falk, and the dampers are 
opened. By means of weights on the lever the regulator can 
be set to operate at any pressure. The regulator should be 
connected to the boiler below the water-line, or by means of 
a U-shaped pipe, arranged so that the part of the vessel below 
the diaphragm will remain full of water; otherwise the heat 
in the steam will cause the rubber to deteriorate rapidly. The 
form shown in Fig. 171 is so arranged that the diaphragm must 
in every case be in contact with water. 

While rubber diaphragms are usually durable for low-pres- 
sure steam-regulators, still they occasionally are ruptured. In 
order to prevent accident from such a cause, the Xason Manu- 




SETTINGS AND APPLIANCES. 225 

facturing Co. have devised a form of such a character that the 
draft-doors will close, instead of open, in case of rupture- This 
is done by using a link in the connecting-chain to the draft- 
doors of some metal that will be fused at a temperature below 
that of boiling water, and arranged so that in case of rupture 
the escaping steam and hot water will impinge upon and melt 
it; the damper will be closed by its own weight when the link 
breaks. 

Damper-regulators for high-pressure steam are constructed 
so as to operate on the same principle as those described, but 
instead of a rubber diaphragm, either a metallic diaphragm or a 
piston working in a cylinder, and operated by water-pressure, 
is employed. 

The following cut shows the external appearance of one of 
the many forms in use: 




Fig. 171. — Piston Damper-r^ulator. 

93. Blow-off Cocks or Valves. — Every steam-boiler should 
be provided with an appliance for emptying all of the water 
when desired. This may be done by leading a pipe from the 
lowest part of the boiler and providing a cock or valve so that 
it can be discharged at pleasure. The pipe leading from the 
boiler should have a visible outlet, so in case there is any leak 
it can be seen and stopped. The writer prefers a cock to a 
valve for use on the blow-off pipe, since it is less likely to be 
stopped by scale or sediment from the boiler. 

In case the water of condensation from the heating coils 
is not returned to the boiler it is necessary to blow off some of 
the water very frequently in order to lessen the deposition of 
scale or dirt on the bottom of the boiler. 



226 HEATING AND VENTILATING. 

94. Form of Chimneys. — ^The form and size of the chim- 
ney is of great importance in connection with the satisfactory 
operation of a heating plant, and it should in every case 
receive the closest inspection before guarantees of capacity 
are made. 

It will be found that for a specified area a roimd chimney 
will have the greatest capacity, but in ordinary building con- 
struction such a chimney is difficult to construct and is not 
ordinarily built. A square chimney of the same area has some- 
what more friction, and one with a rectangular narrow flue 
very much more, so that an increase in area proportional to 
excess of perimeter should be made for such cases. The chimney 
should be as smooth as possible on the inside in order to pre- 
vent loss of velocity by friction, and, if of brick, the flue should 
in every case be plastered. In the construction of chinmeys it 
is better that the inside be made with a thin wall not connected 
in any way with the outside, both in order to permit free expan- 
sion of the inner layer of the chimney with the heat and also 
to secure the advantage of the non-conducting power of an air 
space between the inside and outside walls. Such a construc- 
tion is common for chimneys for power purposes, but is not 
ordinarily applied to those used in buildings. 

95. Sizes of Chimneys. — The area of cross-section required 
for a given chimney will depend upon its height and also upon 
the amoimt of coal to be burned. The conditions which affect 
chimney draft are so numerous, and so difficult to consider in 
any theoretical discussion, that empirical or practical formulas 
derived from the study of actually existing plants are prob- 
ably more satisfactory than those obtained from purely theo- 
retical computations. Of the various formulae which have 
been given for the capacity of chimneys the writer prefers 
that of William Kent, from which the accompanying table is 
computed. 

Kent's formula is computed on the assumption that the chinwiey 
shall have a diameter two inches greater than that required for passage 
of the air, in order to compensate for friction. The following is his 
formula: 



SETTINGS AND APPLIANCES. 



227 



in which i4= actual area of the chimney in square feet, JS= effective area, 
/i« height in feet, 5= side of the square in inches, -ff= horse-power of plant. 
If wc let i?= number of square feet of radiating surface to be supplied, 
then, Article 73, page 190, 



from which E'= 



0.003/2 



100 



The table gives the diameter of round or side of square chinmeys in 
inches for various heights computed from the above formulae, with the 
diameter increased by 2, to allow for friction. A square chimney is con- 
sidered the equivalent of the inscribed round one. 

DIAMETER OR SIDE OF CfflMNEY IN INCHES REQUIRED FOR 
VARYING AMOUNTS OF DIRECT STEAM-RADIATING SURFACE. 



Height of Chimney 
in Feet. 


20 


30 


40 


SO 


60 


80 


100 


120 


Square Feet of 
Steam Radi- 
ation. 


Horse- 
power. 


















250 


2.5 


7-4 


7.0 


6.7 


6.4 


6.2 


6.0 


6.0 


6.0 


500 


50 


9.6 


9.2. 


8.8 


8.2 


8.0 


6.6 


7.3 


7.0 


750 


7-5 


II 3 


10.8 


10.2 


9.6 


9 3 


8.8 


8.5 


8.2 


1,000 


10. 


12.8 


12.0 


II. 4 


10.8 


10.5 


10. 


9 5 


9.2 


1,500 


150 


15-2 


14.4 


13 4 


12.8 


12.4 


"5 


II. 2 


10.8 


2,000 


20.0 


17.2 


16.3 


IS 2 


14. 5 


14.0 


13 2 


12.6 


12. 1 


3,000 


30.0 


20.6 


18-5 


18.2 


17.2 


16.6 


15.8 


150 


14.4 


4,000 


40.0 


23.6 


22.2 


20.8 


19.6 


19.0 


17.8 


17.0 


16.3 


5,000 


50.0 


26.0 


24.6 


23.0 


21.6 


21.0 


19.4 


18.6 


18.0 


6,000 


60.0 


28.4 


26.8 


25.0 


23 4 


22.8 


21.2 


20.2 


19-5 


7,000 


70.0 


30.4 


28.8 


27.0 


25. 5 


24.4 


23.0 


21.6 


20.8 


8,000 


80.0 


32.4 


30.6 


28.6 


26.8 


26.0 


24.2 


234 


22.2 


9,000 


90.0 


34 


32.4 


30.4 


28.4 


27.4 


25.6 


24.4 


234 


10,000 


100. 


37 


34 


32.0 


30.0 


28.6 


27.0 


254 


24.6 


15,000 


150 


.... 


• • • • 


384 


36.2 


35 


33 


310 


29.2 


20,000 


200.0 


.... 


• • • • 


43 


42.0 


41 .0 


37.0 


350 


34.0 


30,000 


300.0 


.... 


.... 


.... 


50.0 


48.0 


46.0 


43 


41.0 



For other 
factors: Hot 



kinds of heating multiply the radiating surface by 
■water heating 1.5, indirect steam 0.7, hot-blast 



the following 
heating 0.2. 



22S HEATINLi A>D VENTILATIXG. 

g6, ChimnejMofB*— Th^ cnft of a chimney is influenced 
lv> ;i ^^rt\il extent by ihe ooncitiocs of the surrounding space. 
If v^ihcr buiAiinc? e-\:>: ir. the \-icinity of such a form as to 
dotlect the currents c: i:r i.-srn the chinuiey. the draft will be 
in*it\urcvi J-nd r.uy S? entirely destroyed. The objects which 
tend iv^ prvv.uoe vicAT.-a-iro* iir-currents may sometimes be 
siluati\! .1 v.vn<:oeniV*e cistJ-nce fron™. the chimney and thus 
reiuler the >:xvirle cause c: roor vinift ver\- difficult to deter- 
mine. The ren;edv for a >n:o£v chinr.nev is sometimes difficult 
to apply, but usudl'.y the drift will be improved, first, by 
iiureasini: ihe heiiiht o: the chhr.ney: second, by adopting 
Si>ine form of chin:r.ey-:o:^ which utilizes the force of horizontal 
currenls to aid by invius.::. n in increasing the draft. 

The writer founvi t'r.a: cur.ed trumpet-shaped tubes located 
with the small ends pro'eviing into the chimney in an upward 
ilirection iiureast\i the draft materially when the wind was 
blowini: iiuo the o^vnincs. and there is little reason to doubt 
hut that a chiir.nev-top n:av be constructed in such a manner 
as to nialeri.illv iiuTea><* :he draft. 

gy. Grates. For suivvrtini: the fuel during its combus- 
tion in such a ir..ir.ner as lo allow a free passage of air, a per- 
forated ir.elallic construction of sv^n'.e sort is required. For 
luuinui; N cry line cvul the jvrforations must be small and close 
to'.cihcr: fi>r burnini: larLrer sijcvl co.i! the perforations may be 
Lni^er and further apart. The area of the air-spaces compared 
with the total area of the i^rate should be about 50 per cent in 
order to secure best results, but they will more generally be 
fovuid to be ,^c to 40 per cent. The grates are usually con- 
structed (>f cast iron anil in a great variety of forms, as 
shown in Figs. 173 and 174. In some instances a series of 
parallel bars is useil; in others the grates are made in one solid 
casting. This latter practice is never one to be recommended. 
The solid grate is likely to break from expansion strains due to 
heating unless made in such form that the various parts are 
free lo expand independently. 

Nearly all heating-boilers, hot-water heaters, and furnaces 
are supplied with some form of shaking- and dumping-grate. 



SETTINGS AND AFPLIANCBS. 



229 



Many of these grates are known from experience of the writer 
to give most excellent satisfaction, and doubtless all present 
points of merit. The various shaking-grates operate in nearly 
every way, and it is hard to conceive either a form of grate- 
bar or a method of shaking which is not exemplified in some 
of these grates. Some of the bars are flat or rectangular in 
shape, and are operated by shaking backward and forward; 
others are triangular and are occasionally rotated so as to pre- 
sent successively new surfaces to the lire each time they are 
shaken. The shaking-grate will, in general, be found much 
superior to the fixed one, and a furnace fitted with such grates 
is more easily managed and more cleanly than one with a fixed 
grate of any description. 

Hard coal, stove or egg size, is the standard fuel upon which 





Fig. 173. Fig. 174. 

Different Forms of Grates. 



boiler capacities are usually based. For pea or buckwheat coal, 
a larger grate is necessary, as the smaller sizes pack closer, 
choking the draft and burning coal slower. For anthracite 
coal, the heating value falls off approximately proportional as 
the percentage of the ash increases, so that an excellent check 
on the quality >of the coal and the efficiency of the grate is the 
relative amount of ashes produced. 

The smaller sizes of coal are cheaper but require more care 
in firing and the saving in price may be easily offset by coal 
dumped through with the ashes. The small coal is hard to 
force in severe weather, but holds the fire better in mild weather. 
Soft coals are objectionable on account of the smoke and soot 



230 



HEATING AND VENTILATING. 



m 



produced and are not much used for household heating except 
where anthracite is commercially unobtainable. 

98. Traps. — In all systems of gravity steam-heating, the 
water of condensation returns directly to the boiler, and no 
appliance either for maintaining a water-line in the building or 
returning the condensed steam to the boiler is required. But 
there are cases in which it is necessary to maintain the water- 
line at a certain definite height, and also to prevent the escape 
of steam without interfering with the discharge of condensing 
water. For this purpose a steam-trap is required. One form 

of a steam-trap which has always been used 
to a greater or less extent for this purpose 
is a siphon made in the shape of a U bend, or 
its equivalent of pipe and fittings, as shown 
in Fig. 175. It consists of two legs, AB and 
BCy which may be close together or any 
distance apart, but the length of which must 
be sufficiently great to prevent pressure acting 
through the pipe FA forcing the water out 
of BC. CE is a vent-pipe extending to the 
air; Z7 is the discharge for the condensed 
water. In ordinary operation the leg CB is 
filled with water which is constantly over- 
flowing, and AB with steam and water, the total 
pressure in both legs being in each case equal. 
The siphon-trap may be open to the objection that it will 
require a great deal of vertical room if the pressure is great; 
for this reason traps with mechanical movements of some kind 
are usually preferred. The simplest of these traps contains a 
float (Fig. 176) which rises and falls with change of level of the 
water in the vessel. Rising above a certain point, it opens a 
discharge-valve; falling below, it closes it. Traps of this class 
are made of a great many designs. In some instances traps 
are made as in Fig. 177, in which a weight IV is used instead of 
a float and is nearly counter-balanced by the weight D. As the 
water rises in the trap it tends to lift the weight \V with a force 
equal to weight of water displaced, thus opening a discharge- 



B 
Fig. 175. 
Siphon-trap. 



SETTINGS AND APPLIANCES. 



231 



valve at B. WTien the water falls, the valve is closed. It is 
noted that the counter-weight D is always above the water- 
line. 

A large number of traps are made with a hollow metallic 
float or bucket, so arranged as to open a valve when the bucket 




Fig. 176. — Float-trap. 

is full of water. One form is shown in Fig. 178, in which the 
water enters the trap at A, filling the space 5 between the bucket 
and the walls of the trap. This causes the bucket to float, and 
thus to close an orifice in the discharge-pipe V. When the 
water rises above the edges of the bucket it flows into it and 
causes it to sink, which opens the discharge-valve at V. The 




Fig. 177. — Counter- weighted Trap. 

water is forced out through the pipe B by the steam pressure 
acting on the surface SS. 

The bucket traps are made in great variety, both as to 
form of valve, guides for bucket, etc. Fig. 179, shows one 
of the traps which is in common use, with all details of con- 
struction. 

Another extensive class of traps are made so as to be closed 
by the expansion due to increase in temperature. These traps 



HEATING AND VENTILATING. 

differ from each other very 
much in form; the principle, 
however, is in all cases the 
same. Thus in the diagram, 
Fig. i8o, steam is supplied at 
A and discharged at B. The 
bent springs S are prevented 
by guides from moving later- 
ally, so that the expansion 
due to heat causes a motion 
which closes the orifice in the discharge-pipe B. When the 
water in the trap cools the valve opens. The materials 
used for traps of this class can be metallic or some compo- 




FiG. 178.— Bucket Trap. 




Fig. 179.— Bucket Trap. 

sition of material like that employed for air-valves. The dis- 
charge can be arranged to take place from the bottom or, as 
shown in the diagram, from the side. 

Traps which combine 
one or more of the prin- ,—l-,,^ 

dples of operation as de- jcIZ^ 

scribed are on the market. 
Thus Fig. 181 represents a Fic. iSo.— Expansion-trap. 



SETTINGS AND APPLIANCES. 2 

trap with two valves in which one valve is opened by expansion, 
the other by a float. 

The bucket traps have generally proved the most rehable 
and less likely to be injured by use. The float-traps have been 
liable to failure because of leakage of the float, but recent 
improvements in manufacture render this accident quite improb- 
able. All traps need periodical inspection, as the valves are 
likely to become more or less choked up, in which case the trap 
may fail to operate. AU of the traps described wiU discharge 
the water to a height which corresponds to the steam-pressure 
in use, and hence when used with high-pressure steam will lift 
water to a considerable distance; but in no case will they 




Fig. i8i. — Combined Float- and Expansion -trap. 

return the water into the boiler from which the steam was 
received. For this purpose a trap of considerable more com- 
plexity, known as a return-steam trap, must be used. 

951. Return-traps. — Traps which receive the water of con- 
densation and return it to a boiler ha\'ing considerably higher- 
pressure steam than that acting on the returns, are known as 
return-traps. They are made in quite a variety of forms, but 
the general principle of operation is shown by the diagram 
Fig. 182. In this figure D represents the boiler and AB the trap, 
which is located above the boiler and is supplied with steam 
from the boiler at -4. It is connected with the return system 
by a pipe leading from the tank or drum P, and pipe discharging 
into the trap at E. A pipe leads from the bottom of the trap 



234 HEATING AND VENTILATINfi. 

B and connects below the water-line with the boiler. Check-J 
valves are located at C and C, which permit the flow to t 




Fic. i8j.— DiagE»m Showing Action of Return-ti^. 

place toward the boiler only. The essential method of opt 
tion of the trap is as follows: First, water flows into the trap 




FiG- 1S3. — The accotnpanyiDg engraving shows a crosr^eciioooJ view of (lie Mov 
head Tilling Relurn Trap with parts removed and broicen away ^ 
the water inlet and discharge ogtenings. and also the manner of d 
live steam From boiler lo a point above the h*De of condensatioQ in trap. 
arrows indicate the direction taken by the condcnsaticHi on entering aiid k 
ing and the steam on entering the trap. 

from the return P, until it reaches a certain level, when it a 
on the float £ so as to open a balanired steam-valve, called a 



SETTINGS AND APPLIANCES. 



235 



equalizing-valve, connected to the main pipe A. This permits 
steam from the boiler to enter the trap, which equalizes the 
pressure of steam in the trap and boiler. The water in the trap, 




. — Gravitating Return- imp. 



because of its greater density, then commences to flow out 
through the pipe B. and need only cease when the level becomes 
nearly the same as in the boiler. The discharge of the water 




F(0. i«5.— Buncly Return Trap. 

causes the float B to fall, which closes the equalizing-valve, and 
the operation as described is again repeated. 

The accompanying engraving shows a cross-sectional view 



236 HEATING AND VENTILATING. 

of the Morehead Tilting Return Trap with parts removed and 
broken away to disclose the water inlet and discharge open- 
ings, and also the manner of delivering live steam from boiler 
to a point above the line of condensation in trap. The arrows 
indicate the direction taken by the condensation on entering 
and leaving and the steam on entering the trap. 

Instead of a float a bucket may be used to operate the equaliz- 
ing-valve, acting in a manner similar to that described for the 
ordinary bucket trap. 

The bucket is probably superior to the float for this pur- 
pose, since it is less likely to be affected in its operation by 
change in density or pressure of the steam. 

Various other systems for opening and closing the equal- 
izing-valve have been adopted, of which one, shown in Fig. 184, 
consists in mounting the trap so that it will move into one 
position when empty and into another when fuU, the motion 
so obtained being used to open and close the equalizing-valve. 

A different construction for accomplishing the same pur- 
pose is sho^Ti in Figs. 183 and 185. 

100. General Directions for the Care of Steam-heating 
Boilers. — Special directions will be no doubt supplied by the 
maker for each kind of boiler, or for those which are to be 
managed in a peculiar way. The following directions are gen- 
eral and should always be obser\'ed, regardless of the kind of 
boiler employed : 

1. Before starting the fire see that the boiler contains water. 
Its surface should stand a distance of from one-third to one- 
half the height of the gauge-glass. 

2. See that the smoke-pipe and chimney-flue are clean and 
that the draft is good. 

3. Build the fire in the usual way, using a quality of coal 
which is adapted to the heater. 

4. In operating the fire keep the fire-pot full of coal and 
shake down and remove all ashes and cinders as often as the 
state of the fire requires it. If a magazine heater is used it 
must be kept full of coal. 

5. Hot ashes or cinders must not be allowed to remain in 



SETTINGS AND APPLIANCES. 237 

the ash-pit under the grate-bars, but must be removed at stated 
intervals to prevent burning out of the grate. 

6. To control the fire, see that the damper regulator is 
properly attached to draft-doors and damper; then regulate the 
draft by weighting automatic draft-lever as required, lightly or 
not at all in mild weather, but increasing as the weather be- 
comes colder. 

7. Should the water in the boiler escape, by means of a 
broken gauge-glass or other mishap, it will be safer to dump 
the fire and let the boiler cool before letting in cold water. 

In no case sliatdd an empty boiler be filled when hot. If the 
water gets low, but not out of sight in the gauge-glass, extra 
water may be added at any time by the means provided for 
that purpose. 

8. Occasionally lift the safety-valve from its seat to see that 
it is in good condition. 

9. Clean the boiler, if used in a gravity system of circula- 
tion, once each year by filling with pure water and emptying 
through the blow-off pipe. If the steam is used largely for power, 
the boiler must be cleaned at frequent intervals. In case the 
boiler should become foul or dirty it can be thoroughly cleaned 
by adding a few pounds of caustic soda and allowing it to stand 
one day, then emptying and thoroughly rinsing. Kerosene 
oil will loosen boiler scale and not injure the boiler, but its 
odor will be quite likely to penetrate the whole building in 
which the heating system is located. 

10. During the summer months the writer would recom- 
mend that all the water be drawn off from the system and 
that air-valves and safety-valves be opened, to permit the 
heater to dry out and remain so. Good results are, however, 
obtained by filUng the heater full of water, driving off the air 
by boiling slowly, and allowing it to remain in this condition 
imtil needed in the fall. The water should then all be drawn 
off and fresh water added. 

11. Keep the fire surfaces of the boiler clean and free from 
soot. For this purpose a brush is provided with most heaters. 

12. In case any of the rooms are not heated, look out for 



238 HEATING AND VENTILATING. 

the steam-valves at the radiators. If a two-pipe system, both 
valves at each radiator must be opened or closed at the same 
time, as required. See that the air- valves are in proper condi- 
tion. If a one-pipe system, one valve only has to be opened 
or closed. 

13. If the building is left imoccupied in cold weather, draw 
all the water out of the system, which can only be done by 
opening blow-off pipe, all radiators, and air-valves. 

Id. Care of Hot-water Heaters. — The general directions 
for the care of steam-heating boilers, apply in a general way 
to hot-water heaters as to the methods of caring for the fires 
and for cleaning and filling the heater. The special points of 
difference only need to be considered. All the pipes and radi- 
ators must be full of water and the expansion-tank should 
contain some water, as shown by the gauge-glass or by the 
pressure-gauge; and this condition should be determined before 
building a fire and whenever visiting the heater for the pur- 
pose of replenishing the fuel. Should any of the radiators not 
circulate, see that the radiator valve is open, then open air- 
valve imtil the water runs out, after which it must be closed 
tight. Water must always be added at the expansion-tank 
when for any reason it is drawn from the system. 

102. Boiler ^Explosions. — Boiler explosions sometimes occur 
with disastrous results. They are not limited to boilers in 
which high-pressure steam is employed, but also occur in some 
instances with low-pressure boilers employed in heating. 

The cause of a steam-boiler explosion is in every case an 
excess of pressure above that of the strength of the boiler. 
The effect of this is primarily to rupture a part or portion of 
the boiler, relieving the pressure on the side of the rupture. 
This leaves unbalanced all the pressure acting on the opposite 
side of the boiler, which may be suflScient to project- the boiler 
into the air with considerable velocity. As showing the amount 
of force which exists even with small pressures we would have 
for each square foot of the boiler with 10 pounds pressure 
above the atmosphere a force of 1440 pounds per square foot 
of surface, applied to move it as a projectile. If the pressure 



SETTINGS AND APPLIANCES. 



239 



were ten times as great the force would be ten times greater, 
and the effect many times worse. The disaster caused by the 
explosion would depend largely upon the suddenness with 
wliich this force was applied; if it were applied gradually no 
bad results might follow; if applied instantly the results might 
equal the explosion of a large amount of dynamite. Boilers 
sometimes explode because of defective material, poor con- 
struction, or overheating of parts; they also sometimes explode 
because of defects in the safety-valve or in the appliances for 
showing the true level of the water; but in all cases the immediate 
cause of the explosion is over-pressure. The causes which 
lead to the formation of steam with a pressure in excess of that 
of the strength of the boiler are various; one of them is the prac- 
tice of permitting the water in the boiler to get low and then 
supplying feed-water, which because of the highly heated 
condition of the surfaces is rapidly converted into steam, caus- 
ing the pressure to become excessively high. 

It is not necessary to suppose that boiler explosions are 
caused by any mysterious force which is suddenly developed 
in the boiler. On the other hand, the amount of force which is 
stored in the hot water and steam is sufficient to produce at 
any time a terrific explosion, provided the necessary opportu- 
nity is presented. Dr. R. H. Thurston has computed the 
energy stored in various classes of boilers under the ordi- 
nary conditions of working, and the table on p. 240 shows 
some of the principal results of that calculation and will give 
some idea of the enormous force stored in heated water and 
steam. 

Considering the total number of heating-boilers in use in 

the United States the number of explosions is very small, so 

thi^i^BkAippose no improvement in construction over the 

"^WWI^^WIkwIs, the risk which any person would run is very 

•ans quite probable that if one were to use a 

as the average boiler, the chances would 

die until killed from this cause he would 

old; that is, estimating from the total 

use for heating, as compared with the 




240 



HEATING AND VENTILATING. 



number of explosions of such boilers, the chances are that 
one per year in ten thousand would explode. 

Some disastrous explosions of heating-boilers have, how- 
ever, occurred in the United States, of which may be men- 
tioned that at the Central Park Hotel, Hartford, Feb. 17, 1889, 
in which fifteen people were killed and the hotel entirely de- 
stroyed; also the boiler explosion at St. Mary's Church, Fort 

STORED ENERGY OF STEAM-BOILERS.* 



Type. 


Pressure. 

Lbs. per 

Sq. In. 


Rated 

Power. 

H.P. 


Total 

Stored Energy 

Available. 


Energy 
per Lb. of 

Boiler. 
Ftxjt-lbs. 


Maximum 
Ht. of 

Proj'fnof 

Boiler. 

Feet. 


Initial 

Velocity. 

Total. 


I . Plain Cylinder. . . . 


100 


10 


47,281,898 


18,913 


18,913 


606 


2. Cornish cylinder. . 


30 


60 


58,260,060 


3,431 


3,431 


290 


3. Two-flue cylinder. 


150 


35 


82,949,407 


12,243 


12,243 


625 


4. PLiin tubular 


75 


60 


51,031,521 


5,372 


5,372 


430 


5. Locomotive 


125 


525 


54,044,971 


2,786 


2,786 


375 


6. ** 


125 


650 


71,284,592 


. 2,851 


2,851 


379 


7. '' 


125 


600 


66,218,717 


3,219 


3,219 


397 


8. ** 


125 


425 


65,555.591 


4,677 


4.677 


455 


9. Scotch marine .... 


75 


300 


72,734,800 


2,687 


2,687 


348 


10. .... 


75 


350 


109,724.732 


2,889 


2.889 


356 


II. Flue and return.. . 


30 


200 


92,101,987 


1,644 


1,644 


245 


12. ** *' ** ... 


30 


180 


104,272.264 


1,862 


1.862 


253 


13. Water- tube 


100 


250 


174,563,380 


5,o^>7 


5,o<)7 


445 


14. *• *' 


100 


250 


230,879,830 


5,130 


5.130 


450 


15. ** '* 


100 


250 


109,624,283 


2,030 


2.030 


.^2S 



* n 



Steam-boiler Explosions, in Theory and Practice," by R. H. Thurston, 



Wayne, Ind., in which the church and priest's house were 
nearly torn down, which occurred Jan. 13, 1886; another at 
Dell Brown's Hotel, Eagle Bridge, N. Y., Dec. 20, 1888, in 
which several people were injured and the building badly 
wrecked; also various other explosions doing less damage. 

It would seem, from a study of the boilers which are injured 
by explosions, that no boiler is entirely free from the disastrous 
effects of an explosion when it is badly managed; but on the 
other hand it also appears that the sectional boilers, or boilers 
in which the water occurs in small quantities, are subject to 
injuries which are comparatively slight and generally easily 



SETTINGS AND APPLIANCES. 



241 



repaired. So far as the writer can find from a study of all the 
explosions recorded in the United States, the water-tube boilers, 
or those with small masses of water, are singularly exempt 
from disastrous explosion. They are, however, quite likely 
to have some part broken away, in which case the pressure 
on the boiler is relieved quickly enough to avert a serious 
explosion. The worst accidents which usually happen to the 
sectional boilers are those due to the burning out of a tube or 
some easily replaceable part. This results ordinarily in a very 
severe leak, which can, however, be repaired. 

The total number of boiler explosions for the United States 
for all classes of boilers average about 255 per year, and as 
reported by the LocomoHvey they were as follows for the ten 
years preceding 1894: 

BOILER EXPLOSIONS IN THE UNITED STATES. 



Year. 


Total No. 
Explo- 
sions. 


Station- 
ary, etc. 


Portable. 


Saw- 
mills. 


Railway 
Locomo- 
tives. 


Steam- 
boats. 


Total 
Killed. 


Total 
Injured. 


1884 


152 


48 


18 


56 


15 


15 


254 


261 


1885 


155 


80 


16 


33 


10 


16 


220 


288 


1886 


185 


88 


16 


45 


22 


14 


254 


314 


1887 


198 


67 


20 


73 


14 


14 


264 


388 


1888 


246 


104 


30 


69 


23 


20 


33^ 


505 


1889 


180 


85 


21 


56 


15 


13 


304 


433 


1890 


226 


94 


16 


75 


25 


16 


244 


351 


1891 


257 


"5 


35 


68 


22 


17 


263 


371 


1892 


269 


122 


24 


79 


33 


II 


298 


442 


1893 






245 








220 


151 



The following table gives the total number in Great Britain 
for about the same time: 



BOILER EXPLOSIONS IN GREAT BRITAIN. 



Years. E 


Explosions. 


KiUe 


1882-83 


45 


35 


1883-84 


41 


18 


1884-85 


43 


40 


1885-86 


57 


33 


1886-87 


37 


24 


1887-88 


61 


31 


1888-89 


67 


33 



Years. 


Explosions. 


Killed. 


1889-90 


77 


21 


1890-91 


72 


32 


1891-92 


88 


23 


1892-93 


72 


20 



Total 660 313 

Ratio 482 



242 



HEATING AND VENTILATING. 



This table would scan to indicate that the explosions in 
this country were more disastrous, so far as taking life is con- 
cerned, as in this country two 
people were killed for about every 
three explosions, whereas in Ger- 
many and Great Britain we have 
about twice as many explosions 
as deaths. This is probably due 
to the fact that the statistics in 
this country classify as boiler ex- 
plosions only those which are 
markedly disastrous, whereas in 
France and Germany every leak 
or break which appears from this 
cause is recorded as an explosion. 

As showing the disastrous effects 
often produced by a boiler explo- 
sion, the following is abstracted 
from Thurston's "Manual of Steam- 
boilers." Fig. i86 shows the boiler- 
loom before the explosion. The boiler was made of ^ iron, 




'".^-^ — 


_.,.' 


, — .< 


'\~-~~ 


■— i / 




ISR* 




L > U / ^ 




mWi^Si 


'- — >i 


^fek. 




ib 


^^ 


RR^ilM'tiii 




mplpp 


^KirTE^ 


1^^ 








WM. 


""^^sB 



Fig. 187.— Path taken by the Boiler, 
was 3 feet in diameter, and was 7 feet high; the upper tube- 
head was flush with the top of the shell, the lower forming 



SETTINGS AND APPLIANCES. 243 

the crown of the furnace, which was about 2 feet above 
the grates and the base of the shell, and was flanged upon 
the inner surface of the furnace. There was a safety-plug 
in the lower tube-head which was not melted out. The 
working pressure was 60 pounds per square inch, and the 
explosion probably took place at or a little below this pres- 
sure, throwing the boiler through the roof and high over a 
group of buildings and a tall tree close by, finally burying 
itself half its diameter in the frozen ground. There had 
been a leak in the lower head which had reduced by erosion 
the thickness of the tubes and the lower head, so that the 
pressure was sufficient to force the lower head down away from 
the tubes, opening fifty or more holes 
2 inches in diameter from which the fluid 
contents of the boiler issued at a high 
velocity, relieving the pressure below 
and converting the whole boiler into a 
great rocket weighing about 2000 pounds, l^ 

103. Explosions of Hot-water Heaters. 
— ^While hot-water heaters provided with 
an open expansion-tank are to a great 
extent free from the dangers of explosions, still it is quite pos- 
sible that extreme carelessness in erection, the freezing up 
of connections to expansion-tank, or other mishaps, might 
render the apparatus fully as dangerous as the steam-boiler 
under its most unfavorable conditions. Some very disastrous 
explosions have occurred of hot-water heating plants when 
operated under the Perkins or high-pressure system, and it 
seems quite probable that such a system, even under the most 
favorable conditions, is more dangerous than the steam-h'eating 
system. The hot-water heating system should be so con- 
structed that the connection between the expansion-tank 
and heater cannot by any possible means be closed. The 
placing of a valve in this connection was the cause of a 
very disastrous explosion in a residence in New York City 
several years ago, and emphasizes the necessity for caution 
in this respect. 



y 



244 HEATING AND VENTILATING. 

104. Prevention of Boiler Explosions. — ^Boiler explosions 
are probably preventable in every single case by using, first, 
boilers properly designed, and constructed of excellent material 
and with goqd workmanship; and second, by seeing that all 
appliances, as safety-valves, blow-off cocks, feeding apparatus, 
etc., are in excellent order; and third, by providing skilled and 
intelligent attendance. 

Disastrous results are usually almost entirely prevented by 
the use of sectional boilers, and for heating purposes there 
are at the present time comparatively few of any other kind 
in use. 

As a rule heating-boilers, especially those of small sizes, 
are not under close supervision, but are attended to and visited 
only at comparatively long intervals. For this reason auto- 
matic appliances for feeding the boiler and for regulating the 
pressure, opening and closing the dampers, are usually supplied; 
hence the person erecting the plant should exercise the utmost 
care to see that such appliances are in excellent order and of 
such character as are likely to prove durable and reliable. 
While it is quite certain from our statistics that not one boiler 
out of ten thousand is likely to explode per year, yet neverthe 
less the contractor should always bear in mind that a steam- 
boiler is in every case a magazine of stored energy, and if badly 
constructed, poorly erected, or carelessly managed may do an 
inmiense amount of damage. 

To insure safety it is better to specify that, " All steam- 
heating boilers and hot-water heaters and their appurtenances, 
which are not provided with an effective device limiting the 
pressure carried to fifteen pounds to the square inch, shall 
conform to the Rules formulated by the Massachusetts Board 
of Boiler Rules. Steam-heating boilers and hot-water heaters 
and their appurtenances, not carrying a pressure in excess 
of fifteen pounds to the square inch, shall be provided with 
such appliances to insure safety as to conform to the Rules 
formulated by the Massachussetts Board of Boiler Rules/* 



CHAPTER X. 
GRAVITY STEAM-HEATING SYSTEMS. 

105. Systems Employed in Steam-heating. — ^There are in 
general two systems of heating, known as the gravity return, 
and the pump return heating systems. In the first of these, the 
gravity system, the water of condensation from the radiators 
flows by its own weight into the boiler at a point below the 
water line, either with or without traps or separate drips; 
in the second the water of condensation does not flow directly 
into the boiler, but is returned by some special machinery or 
else wasted. The second class of steam-heating systems includes 
most of the high-pressure steam-heating systems and many of the 
various systems of vacuum, vapor, or atmospheric steam heating. 

In the high-pressure systems steam of any pressure can be 
produced in the boiler, of which a portion may be employed 
in operating engines, elevators, etc. High-pressure steam is 
seldom used in the radiators, low-pressure steam being obtained 
either directly from the boiler or by throttling or passing 
through a reducing valve, or, in some instances, by using the 
exhaust steam from engines or pumps. In general the dif- 
ferent types of vapor, vacuum, or atmospheric steam-heating 
systems regulate the amount of heat delivered by the radiator 
by changing the absolute steam pressure, or by varying the 
amount of air present inside the radiator by special traps, 
air-valves, or other special devices in the air (or water) dis- 
charge line from the radiator. 

In this chapter we shall discuss the amount of heat and 
radiating surface required for the gravity circulating system of 
steam heating in detail, reserving the next chapter for the other 
systems of steam heating. 

245 



246 HEATING AND VENTILATING. 

The preceding classification is independent of the pressure 
carried in the heating system, and a vacuum heating system 
will fall into the first or second of these classes depending upon 
whether the condensed steam returns to the boiler by its own 
weight or not. The vacuum system, in which the condensate 
is pumped back or wasted, will be treated in the next chapter. 

io6. Definitions of T^ms Used. — Certain terms have been 
adopted which are always used to describe definite parts in a 
system of piping, as follows: 

The main or distributing pipe is the pipe leaving the boiler 
or heater and conveying the heated products to the radiating 
surfaces. In steam-heating this is termed the main steam-pipe, 
and in hot-water heating the main flaw-pipe. It may be car- 
ried from the boiler without branches to the top of the build- 
ing (Fig. 189), where the distributing pipes are taken off, or it 
may run in a horizontal or vertical direction from the heater, 
and branch pipes taken off as required. The pipes in which 
the flow takes place from the radiating surface toward the 
boiler are called return-pipes.. The pipes which extend in a 
vertical direction are termed risers; when the flow in these 
pipes is downward they are called return-risers. 

A relief or drip is a small pipe run from a steam-main, so 
as to convey any water of condensation to the return; it must 
be employed at all points where water is likely to gather. 
For illustration of use see Fig. 192. 

Pitch is the inclination given to any pipe when running in 
nearly a horizontal direction. In general the inclination or 
pitch of a supply-pipe should, in steam-heating, be downward 
from the boiler, and arranged so that the water of condensa- 
tion will move in the same direction as the current of steam. 
In hot-water heating the pitch should be upward from the 
boiler. In all return-pipes the inclination should be down- 
ward, toward the heater or boiler. 

A relay is a term sometimes used to describe a sudden 
change of alignment, or " jumping up," of a horizontal pipe. 
This is often necessary in a long line of piping to keep the pipe 
near the ceiling and preserve the necessary pitch. At such 



GRAVITY STEAM-HEATING SYSTEMS. 247 

points a drip or relief must permit water of condensation to 
flow into the return. 

Waier-line is a term used to denote the height at which the 
water will stand in the return-pipes. It is usually very nearly 
the same as the level of the water in the boiler, being higher 
only in case there is considerable reduction in pressure due to 
friction. In heating with high-pressure steam it is desirable 
to have all the relief-pipes discharge into a return filled with 
water, so that circulation of steam shall be continuously in 
one direction; this is of less importance with low-pressure 
steam, provided the water which gathers in returns can move 
freely and quickly to the boiler. 

The term siphon is applied to a bend below the horizontal; 
it is sometimes used in the main return to hold water at a dif- 
ferent level from that in the boiler. This is done by admitting 
steam to the top part of the bend on the boiler side by a relief 
from the main steam-pipe. It is similar to the siphon-trap. 
If the relief were not connected to the top of the bend the 
water would pass over by suction into the boiler. 

Steam-traps are vessels designed with valves which open 
automatically so as to preserve the water-level in the returns 
at any desired point. Various kinds are described in Chap. IX. 

Water-hammer is a term applied to a very severe concus- 
sion which often occurs in steam-heating pipes. It is caused 
by water accumulating to such an extent as to condense some 
of the steam in the pipe, thus forming a vacuum which is filled 
by a very violent rush of steam and water. The water strikes 
the side of the radiators or pipes with great force, and often so 
as to produce considerable damage. In general a water-hammer 
may be prevented by arranging the piping in such a manner 
that the water of condensation will immediately drain out of 
the radiator or pipes. 

A bend in the return of a steam- or water-heating system, 
when convex upward, will frequently accumulate air to such 
an extent as to prevent circulation in the system. This is 
designated as an air-trap. When bends of this character must 
be used a small pipe for the escape of the air should be con- 



HEATING AND VENTILATING. 



nected with the highest portion of the bend and led to some 
pipe which will freely discharge the entrapped air. 

An air-valve is not ordinarily to be recommended for such 
situations. 




107. Systems oi Piping. — The systems of piping ordinarily 
employed provide for either a complete or a partial circulat- 
ing system, each consisting of main and distributing pipes and 
returns. Several systems of piping are in common use, of 
which we may mention: 



GRAVITY STEAM-HEATING SYSTEMS. 249 

First, the complete-circuit system, often called the one-pipe 
system, in which the main pipe is led directly to the highest 
part of the building; from thence distributing pipes are run to 
the various return-risers, which in turn connect with the radiat- 
ing surface and discharge in the main return. The supply for 
the radiating surface is all taken from the return-risers, and in 
some cases the entire downward circulation passes through the 
radiating system. 

This system was employed by Perkins in his method of high- 
pressure hot-water heating, and is mentioned by Peclet as 
in use in France in 1830. In this country it seems to have been 
introduced into use by J. H. Mills, and is often spoken of as 
the Mills system of piping. The system is equally well adapted 
for either steam or hot-water heating, and on the score of posi- 
tiveness of circulation and ease of construction is no doubt to 
be commended as superior to all others. It is principally 
objectionable because the horizontal distribution pipes have 
to be run in the top story of the building instead of the base- 
ment, which may or may not be of serious importance. 

Second, a partial-circuit system, in which the main flow-pipe 
rises to the highest part of the basement by' one or more 
branches, from whence the distributing pipes run at a slight 
incline, often nearly around the basement, and finally connect 
with the boiler below the water-line. The radiators are con- 
nected by risers which carry both flow and return from and to 
the distributing pipes, as shown in elevation in Fig. 190 and in 
plan in Fig. 191. This method of piping is employed exten- 
sively for steam-heating, and is perhaps less open to objection 
than any other. 

Third, a system of circulation in which each radiator is pro- 
vided with separate flow- and return-pipes (Fig. 192). In this 
case* the riser and distributing pipes are nm as before, but are 
connected to the return by a drip-pipe; the return is located 
below the water-line of the boiler. The supply-riser from 
each radiator is taken from the main flow-pipe, and the return- 
riser is connected to the main return below the water-level. 
In case two connections are made to a radiator, one for supply 



250 



HEATING AND VENTILATING. 



and the other for the return, it is quite important that ■ 
connection of the return-riser to the main return be made bcIow" 
the water-level of the boiler, in order to prevent steam flowing 
from two directions to the radiator. Such a condition is certain 



■.V,^^^m^ 



I^VVVVVVKV\vU\V^^^?^VVV\^\^^^^ 




to cause water-hummer, as the radiator will retain water aS * 
condensation. 

Various modiflcations of this third system have been used 
from time to time with greater or less success. For instance, 
each radiator has in some cases been connected to a separate 




GRAVITY STEAM-HEATING SYSTEMS. 



251 



flow and return riser, and in other cases simply to a separate 
return riser. These modifications are imimportant and hardly 
worthy of notice. 




a 



-8 

s 

o 

k 

4-1 

•c 

en 



a 



& 



io8. Pipe Connections, Steam-heating Systems. — The 
manner in which branches are taken oflf may have great effect 
on the results obtained in any heating system, since any 
increase in friction in any part of the system will cause the 
flow to be sluggish in that portion, and require more pres- 



252 



HEATING AND VENTILATING. 



sure to induce circulation. The size of pipes required in order 
that resistances may not exceed a certain amount are given in 
the next chapter; but it should be noted that bad workman- 





ss^ssa 



f?>"-B--V. 



—, 7. :^ 



vVNSNS^vVVVVnS 




^vs»>c<c^^csvv^'N^.^cv>'«^ :^^>cvxK>^v:vs:^s:!^c^ & i p^^nxv^^vv xn 




60 



o 
C/3 



a 
5. 

S. 

'a 
6 

I 
o 

M 

o 



ship may defeat the operation of a steam-heating plant having 
the best proportions possible, and that great care is needed, 
(i) to secure the alignment of every part, (2) the absence of air- 
traps or any obstructions whatever which would reduce the 
circulation or make it irregular or uncertain. Some details 



GRAVITY STEAM-HEATING SYSTEMS. 



253 



which are to be considered rather as suggestions than as formal 
directions are given. 

In general, pipe connections should be made so as to afford 
as little resistance as possible to the flow of steam, and in 
such a manner as not to interfere with the expansion of the 
main pipes. The line of piping should present the freest 
possible channels of circulation for the steam as it leaves 
the boiler and for the water of condensation as it returns. 
The expansion, which is not essentially different from i| inches 
for each lOo feet in length, can usually be well provided for by 
the use of two or more right- 
angled elbows substantially 
as shown in Fig. 193. No 
general rule can be laid down 
for all circumstances and con- 
ditions. The following ex- 
amples and illustrations from 
Heating and Ventihtioti show 
the methods of piping com- 
monly employed in setting 
steam-radiators with one-pipe 
connections. Fig. 193 illus- 
trates the method 'where the 
radiator is set close to the 
main and no special drip is 
required. 

The method often em- 
ployed in connecting a riser to a horizontal steam main and 
ruiming a special drip-pipe for condensed water to the return 
main is shown in Fig. 194. 

The method often employed in connecting radiators to 
risers is shown in the upper portion of Fig. 219, The lower 
portion illustrates an essentially different method from that 
shown in Fig. 194 of connecting the riser to the main, and the 
drip-pipe to the return. This method, however, does not allow 
for expansion of the steam main; hence this must be provided 
for in some other portion of its length. 




Fic. 153. — Connection of Radiator from 
Steam Xfain. 



254 



HEATING AND VENTILATING. 



The area of the main pipe must in every case be equivalent 
in carrying capacity to that of all the branches taken oS; it 
consequently may be reduced as the distance from the heater 
becomes greater and as more branches are supplied. Table 
XXII, Appendix, gives the equivalent capacity of pipes of 
different diameters, and can be used in determining the rela- 
tive number of branches of a given size, and also the reduction 
in pipe area which may be made after a certain number of 
branches have been connected. It will, however, in general 




Fig. 194. — Connection 



(rom Main and Return. 



be found, except when large pipes are used, less expensive to 
run the main full size than to use reducing fittings. 

109. Piping for Indirect Heaters. — Indirect radiators have 
been described and methods of setting them illustrated in 
Chapter VII. These radiators are generally set in a case or box 
which is suspended from the basement ceiling and made of 
matched boards lined with tin. The sides of the casing should 
be removable for repair of the radiator. The system of pipes 
which supply the indirect radiators are generally most con- 
veniently erected, like those shown in Fig, 191 or 214 for steam- 
heating, and like that shown in Fig. 224 for hot-water heating. 



GRAVITY STEAM- HEATING SYSTEMS, 



255 



I 



iThe beater should be located above the water-line of the boiler 
I a sufficient distance to afford ready means of draining off the 
' water of condensation. In case this is impossible, a style of 
radiator should be adopted which can be heated by water circula- 
tion. An automatic air-valve should be connected to the 
heater, and every means should be taken to obtain perfect 
circulation to and from the boiler. The chamber which sur- 
rounds the indirect surface is to be supplied with air from the 
, outside by a properly constructed flue. The air passes up 
1 through or over the heater 
and into the rooms by BBJIIj^liiati^yilL-il* ,-.1;^ 
means of special flues, the 
sizes of which are given in 
Chapter V. 

no. Vacuum Circulat- 
ing Systems. — If the air 
could be removed and kept 
from Sowing back in any 
dosed system of steam- 
heating, as, for instance, 
the usual one- or two-pipe 
system of steam drculation, 
in which the return -water 

flows directly to the boiler, we should have conditions which would 
permit a circulation of steam with a pressure above or below the 
atmosphere as desired, and consequently with a pressure and 
temperature dependent upon the amount of fire maintained 
in the heater. Thus, for instance, if so much air were removed as 
to produce an absolute pressure of 2 pounds corresponding to 
a vacuum of about it inches, the boiling temperature, at 
which steam would be produced, would be 126 degrees Fahr., 
and if just sufficient fire were maintained to produce that 
pressure, the temperature would be as stated. If more fire 
were maintained, so as to produce greater quantities of steam, 
the pressure in the system would rise with a corresponding 
increase in temperature. By simple regulation of the fire any 
temperature from 100° to 300° F. could be maintained under 




Fig. igj. — Indirect Surface. 



256 HEATING AND VENTILATING. 

these conditions. Such a system would give all the advantages 
pertaining to low temperatures and regulation of temperatures 
possessed by the hot-water system of heating, and all the 
advantages relating to high temperatures, small radiators, 
and cost of installation pertaining to the steam system. 

Several plans have been devised to produce the results 
described. 

The Morgan system accomplishes the desired result simply 
by the use of an automatic air-valve so constructed that it 
will permit the air to flow out when the steam is at a higher 
pressure than atmospheric in the radiator, but will not permit 
it to return when the pressure is reduced. The air-valve is 
attached in the usual manner to a radiator, a small screen being 
inserted in the connection to prevent dirt passing into the valve. 
The automatic features for permitting the escape of air when 
the pressure is above that of the atmosphere, and preventing 
the escape of steam, consist of a hollow float, one end of which 
is oi>en and submerged in water so as to keep the float nearly 
filled with air. The air thus sealed constitutes a thermostatic 
substance that when expanded by heat causes the float to rise 
closing the opening and thus preventing the escape of steam 
from the radiator; when the temperature falls this air contracts 
and allows the float to fall, thus permitting the escape of the 
air. ■ It is thus seen that the air is expelled from the radiator 
as in the automatic air- valves previously described. To prevent 
the return of the air to the radiator after it has been allowed to 
cool and a vacuum has been formed by condensation, a soft 
rubber ball resting on a rubber seat is employed, which is 
situated near the top of each air-valve and constitutes a check- 
valve opening outward. 

A modified form of the Morgan system, as designed by 
James A. Trane* of Milwaukee, connects the discharge of all 
the air-valves by pipe-lines to a mercury trap or seal located 
near the heater. The air from the system can be expelled by 
pressure through the mercury seal, which, however, acts to 

* The Trane system works equally well if the air-valves at the radiators are 
omitted. 



GRAVITY STEAM-HEATING SYSTEMS. 257 

prevent its return to the system when the pressure falls, thus 
maintaining any vacuum produced by condensation. 

In the operation of the systems which have been described 
for circulating steam at less than atmospheric pressure, the 
valves or checks which prevent the return of the air must in all 
cases be so constructed as not to leak; since any leakage of 
air into the system at any point would destroy the vacuum. 
The problem of constructing every valve or fitting of an entire 
system so as to remain perfectly tight, especially when below 
atmospheric pressure, is a difficult one, consequently all the 
above systems are likely to become inoperative for these reasons. 

As in normal operation the fire is forced in the early morn- 
ing to heat the rooms to 70°, and most of the air is forced out of 
the radiators each day. Consequently, several slight leaks 
which may be plainly visible or audible will not materially 
affect the working of the Trane or similar vacuiun systems. 

III. General Principles. — The general problem of design 
includes the proportioning of, first, the amount of radiating 
surface which will be located directly in the rooms to be 
heated in all systems of direct heating, and in the air-passages 
or flues leading to the rooms in all cases of indirect heating; 
second, the size of the pipes which are to convey the heated 
fluids to the radiating surfaces; and third, the proper size of 
boiler or heater. 

The question of the system or method of heating which is 
to be adopted will usually depend upon considerations of cost 
or of personal preference on the part of the proprietor. The 
various systems of heating, whether by steam, hot water, or 
hot air, as commonly practised in this country, do not often 
come in direct competition. Hot-air heating, where the air is 
moved by natural draft, is adapted only to the smaller sizes 
of dwelling houses, and where heat does not need to be carried 
any considerable distance horizontally. It is generally found 
that if the horizontal distance exceeds 15 or 20 feet the supply 
of heat becomes uncertain in amount. With steam and hot- 
water heating there is no such limitation as to distance; the 
first cost is, however, considerably greater than that of hot air, 



258 HEATING AND VENTILATING. ^M 

but heat can be supplied with certainty to all parts of the sys- 
tem under all atmospheric conditions. Regarding the relative 
merits of systems of steam and hot-water heating, little can 
be said. It will generally be found that the first expense of 
steam-heating is considerably less, and that there is considerable 
difference of opinion regarding the relative economy of oper- 
ation of steam and hot -water heating plants. The tests which 
have been made have generally shown somewhat in favor of 
water.* The difference, however, is not great, and may be 
due to local conditions, but is probably due to the fact that 
the temperature of the discharged gases may be somewhat 
lower for the hot-water heater than for the steam-boiler, and 
also to the fact that in comparatively mild weather the fire in 
the hot-water heater may be regulated somewhat closer, to 
meet the demand for heat. The hot-water system in general 
requires rather better workmanship in the erection of pipe 
lines than steam-heating, and more care must be taken in pro- 
portioning the various pipes and fittings. The heat from hot- 
water radiators is somewhat less in intensity and more pleasant 
than that from steam -radiators, and the temperature can be 
regulated by simply throttling the supply-pipe of the radiators, 
which is not the case with steam. 

Whether direct or indirect heating shall be used will depend 
also on circumstances. It will be found that in general the 
surface requured for indirect heating is one-third to one-half 
greater than that for direct, and it will give off 50 per cent 
more heat per square foot, so that the operating expense is 
practically twice that of direct heating. 

III. Amount of Heat and Radiating Surface Required for 
Warming, — The amount of heat required for buildings of various 
constructions has been considered quite fully in Chapter III, 
from which it may be seen that in ordinary- building construc- 
tion the amount required in heat-units, for each degree dif- 
ference between inside and outside temperature, is approxi- 
mately equal to the area of the glass surface plus one-fourth 

* Sec TransBcIions American Sodcty Mechanical EDgiaeeis, voL s. pftpcr 
by the author. See also report Massachusells Experimenul Stfttioo No. 8, 1890- 





GRAVITY STEAM-HEATING SYSTEMS. 259 

the area of the exposed wall surface plus one fifty-fifth of the 
niunber of cubic feet of air due to ventilation and leakage. 

When results of extreme accuracy are desired the heat 
loss from any room imder consideration may be computed by 
multiplying the area by the loss per square foot as given in 
Chapter III by the difference of temperature and taking the 
siun of the results. I have given in the following pages a 
diagram completed by the late Alfred R. Wolff, for facilitating 
such computation. The approximate method of computation 
in which the assumption is made that a definite area of wall 
surface is equivalent to one foot of glass surface, with the coef- 
ficients as stated, is usually of sufficient accuracy to meet all 
practical requirements. It should be noted that because of 
varying conditions of weather and variations in building con- 
struction, and ignorance of the exact laws of heat transmis- 
sion a certain allowance in calculation is necessary. This 
allowance corresponds very closely to the " factor of safety " 
used in computing structural construction and serves the same 
purpose. In nearly every case the approximate computation 
of building losses as stated in the following rule will result in 
providing radiation correct within the limits of error of the 
coefficients on which the apparently more accurate calculation 
must be based. The approximate rule can therefore be gen- 
erally used with confidence. 

Our knowledge of the coefficient of air leakage through the 
walls of buildings is far from exact yet it is well known that 
leakage of air into a room often has as much to do with the 
requirements for heat as conduction of heat. Until more exact 
data relating to air leakage is obtained it is somewhat absurd 
to expect to compute the heat requirements of a room from an 
exact computation of the heat conducting ability of the walls 
and windows. 

The leakage or infiltration of air into a room through the 
walls and windows is undoubtedly a function of wind velocities, 
difference of pressure inside and out, difference of temperature 
and quality of construction, rather than the volume of the room. 
The data which we have on this subject is obtained by a 



HEAIIXG AND VENTILAl 



comparison of radiation actually needed ^ 
from buQding loss only. This data is i. 
or number of changes of air per hour rath 
of the exposed area. It is probably fairly 
dwellings and small buildings but is to be ■ 
other classes of buildings. The air entering 
with conditions as noted but in direct ht 
appro3cimately equals to three changes p< 
in rooms on the first floor and one in room 

The amount of beat given off by one ! 
ing surface, as determined by a great nui 
is given in Chapter IV, from which it is seen 
radiating surface, with a temperature of i 
surrounding air, i.S heat-units will be { 
foot of surface per degree difference of te 
and when the temperature is i lo above 
about 1,7 heat-units are emitted. 

113. Wolfe's Diagram.— The total heat 
ing surfaces of different characters, correspc 
results of experiments as stated in Chaptei 
diagram, Fig. 196. In this diagram the 
correspond to the mean difference of temj 
air in the room and the radiator, while v 
value of which is read on the scale at 
to the total heat-units transmitted per squ 

To use the diagram assume the differ 
between the air of the room and the ra< 
vertical line until intersection with the 1 
desired condition is found, thence read results on the left. 
Thus, for instance, if the difference of temperature is 150 
degrees the intersection of the line from this |>oint with that 
representing direct ordinary radiation corresponds to 275 heat- 
units, and with that representing i-inch horizontal pipe, 375 
heat-units, as read on the scale at the left. The dotted lines in 
the diagram give the heal transmitted from various indirect 
surfaces for different velocities of the moving air. The results 
are to be found as for direct radiation, but the difference of 



'i 




GRAVITY STEAM-HEATING SYSTEMS. 261 









how 


.T 


Ul hit.l t 






1 


,J.„., 


.... 










-' 


/ 






1 






airM 


"'. 


u 


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vel 


«. 














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•"' 










''".~ 




fair 




r.T 


Bh» 


bir. 


«= 












''' 




/ 


































- 


'/ 


.' 


/ 


/ 


1>I 
































-;/ 


/ 




/ 


/ 
































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/ 




























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■/ 


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/ 






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/ 






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V 


;-' 


/ 








/ 






















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-•/ 


J-' 




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M«»i DJfr.r*iic. gfTiniRiralur* 
Fig. 196. — Diagram of Heat from Radiating Surfaces. 



HEATISG AND VENTILATING. 



temperature is that estimated from the mean of the surroi 
ing air and the radiator. 

Knowing the total heat required for warming and that which 
is given off from one square foot of radiating surface, it is quite 
evideot that the surface required may be computed by the 
process of dividing the former by the latter. 

Many designers of heating apparatus compute the amotmj 
of radiating surface required by approximate " rules-of-thumb " 
which are in current use in their localities. These rules differ 
in many cases very greatly from each other, and often have to 
be modified materially in order to give satisfactorj- results. In 
the application of the more scientific rules which have been 
given there will still always be an opportunity for appljing 
judgment and the results of experience and practice, since it b 
quite impossible that any table of coefficients, no matter how 
extensive, could be given which would apply to all cases ot 
building construction and to all exposures. Allowance for 
unusual conditions are given by Rietschell, Chapter III. 

Certain allowances for unusual construction of buildings are 
often required and must depend upon judgment. 

114. The Amount of Surface Required for Indirect Heating. — 
For tbi^ case the heat received by the rooms is all supplied 
by air which passes over the radiating surfaces and is heated 
by convection. A large number of tests have been quoted 
of these heaters, both with natural and mechanical draft. 
From these experiments it is seen that the amount of heat 
given off by one square foot of surface varies vfith the velocity 
of the air, as shown by the diagram Fig. iq6, the use of which 
has been explained. From Table XVI in Appendix it will be 
noticed that with natural circulation the velocity in feet per 
second will var>' from 2.97 for a height of 5 feet to 8.4 for a height 
of s° feet, and the corresponding convection expressed in 
heat-units per degree difference of temperature per square 
foot per hour, which in the preceding table is termed the 
coefficient, varies from 1.7 to 2,8. 

In indirect systems of heating the warm air enters at a 
temperature 30 to 60 degrees above that in the room and 



.e 




GRAVITY STEAM-HEATING SYSTEMS. 263 

passes out either through the vent-flues or by other means of 
egress at a temperature practically that of the room. In cool- 
ing to the temperature of the room it must surrender sufficient 
heat to balance that lost through the walls and windows. 
Neglecting the slight change in volume due to change in 
temperature, the amount required can be readily computed; 
thus if the entering air be about loo degrees F., one heat-unit 
(B.T.U.) will raise 59 cubic feet one degree; hence one cubic 
foot in cooling thirty degrees will surrender 30/59 parts of a 
heat-unit. Since we require approximately to balance the 
building loss, heat-units equal to the product of the difference 
of the temperature of the room and the outside air, multiplied 
by the glass surface, plus one fourth that of the exposed wall, 
we can find the volume of air required by dividing the result 
by 30/59 for the above case. 

The extent of heating surface in square feet in the radiator 
can be obtained by dividing the total number of cubic feet of 
air as obtained above by the number of cubic feet which may 
be heated the required amount by one square foot of heating 
surface. 

These results are better expressed in shape of formulae from which 
tables suited for practical application may be computed. Let / equal the 
temperature of the room, /' that of the outside air, i" that of the mean 
temperature of the air surrounding the heating surface, V that of the 
heated air, T that of the radiating surface, E the heat required per hour 
per degree difference of temperature to supply loss from the room, a the 
heat given off from i sq. ft. radiating surface per degree difference of tem- 
perature. We have the following formula: 

Loss from the room per hour (/-/' )^= (/-0(G+i^ nearly; . (i) 

Heatbroughtinbyicu.ft.ofairi/s8(r-0; (2) 

Heat given off from i sq. ft. of radiating surface per hour=a(r— /") ; (3) 

Cubic feet of air required per hour= — — -; (4) 

Cubic feet of air heated by i sq. ft. of radiating surface per hour 

i/58(r-o' ^ 

Radiating surface=^^^;^|^^ (6) 



264 HEATING AND VENTILATING. 

TABLE OF FACTORS TO OBTAIN INDIRECT HEATING SURFACF, 
AND OF CUBIC FEET OF AIR HEATED PER SQUARE FOOT OF 
SURFACE PER HOUR. 





B.T.U.— Tot»l H«t 
per Sq. Ft. Hut«. 


Futon for H*atei 
Siirf«e.' 


Co. pt. AirperSq. Ft. 
Hot. Surt. p« floul. 


rtii 


iilf 1 


J 


Hi 


O 


j 


1 


i 

s 


7- 1 ,•■ jT--," 


(I) (l) 1 (i) 1 (4) 


(5) 1 (6) (7) (8) (9) 


(lO) 


(,., 


(I J) 



ROOH 


;o" Fahh., Outside 


ViB 0' Fars., Steam Pkesscre 


LBS., StEAU 




TeWEBATCEE 213* Fahb. 




90 


4S 1 167 


167 


,1,14 


,S»i 


668i.9j!o.96'o 640.48'lo8 


316 JI4 *il 




SO i6» 


16; 


1J4 


486 


6481.4710 7J'o 49:0 361 94 


188 J9;, 376 




5S '57 


"s; 




47' 


6281. 140. 6i|o 4i!o.3i 88 


176 264: 35) 


IIO 


60 1 .5^ 


'S^ 


304 


456 


eo8i,io!o.ss.0 37,o.i8J 7J 


.47I 220 394 



9* 


45 


"74 


"74 3-t8[ 5)' '>96ii 


.73\o 86:o.5i;o,43|"i2 


234 1 336 448 




SO 


itK) 


1601 338 507 


676 I 


.380 69J0. 46.0.341 98 


19^ 394. 39) 


110 


55 


Ib4 


164! 318 491 


656 


.i8o.s6]o.3i»o.2g 86 


173 i6o. 346 


tio 


60 


'SO 


"59; 3i8| 477 


636 


.'6o.S3|o 35'o.'7i 77 


154 )3l! 3C8 



Rook 


60* Fahb., Outside 


^B 0° Fabb., Steau Pbessvbe 


LBS., Steam 


TeUPEKATUBE 313* Fahb. 






80 


40 


173 


"73 344 


5"6 


688li.66|o.83los5lo.4"|'^5 


250 




90 


45 


167 


"67 HI 


501 


668 i,i6|0 58:o.2ojo.39jioS 


2H 








16} 


162 J36 


48C 


652 0.930.460.3,10.53! 94 

638!o.8q|o.43|o 28J0.21I 83 1 


iKt 


382; 376 


IIO 


SS 


■S7 




461 


It* 


349 331 



<J» 


4.5 


IIS 


"'5 >3o| 34S| 460! 


.8 |i.4 !o 93io.7 |74 


.48] 323| 396 




SO 




no 330! 330' 440 


.1311. 060. 700, 53164 


"28 ,92 356 




55 




10s Jioj 31s' 410, 


, 86:0. O3'o.6:!;o. 46:55 


"'O 16s: 320 


110 


60 




100! 200| 300! 400, 


68.0.8JO.S6I0.42U8.5 


97< "45 "04 



90 


45 


"35 


135! 270 405; 540 


361..80 7S057 s 


j .;4| )&"■ 348 




SO 


"JO 


130: 360 390 530, 


780.890.500 54' 7 


1 ISO; 225 300 




55 




1^5, ;50 375 SOO. 


.550 7)o 520 39 W 


■ 133 I9S 264 


I20 


ho 


DO 


120 240 j6o 4S0 




116 174 331 



• To find surface of heater malliply loss from ri 
of ^em^.■ralQrB by the factor for ihe given cond 
fonnula 16). 



c (it-frrcc difference 
lUlts computed by 



GRAVITY STEAM-HEATING SYSTEMS. 



265 



The table on page 264, computed from the above formulae 
for various conditions gives a series of factors which, multiplied 
into the building loss H per degree difference of temperature, 
will give the radiating surface required; il also gives the num- 
ber of cubic feet of air heated the required amount per square 
foot of radiating surface per hour. In the table the term 
coefficient is used for the heat transmitted per degree difference 
of temperature per square foot per hour. 

To use the table, we need simply to know, in addition to 
temperatures, the probable coefficient of heat transmission, 
all other conditions being given. For ordinary indirect heat- 
ing first floor, the velocity of air can be considered as 2 to 4 
feet per second, and the corresponding value of this 
coefficient as 2. For higher floors the velocity is higher, and 
coefficients may be taken as 3. As an example, assume out- 
side temperature zero, inside temperature 70°, and the air 
leaving the indirect radiator at 100°, the factor with which to 
multiply the building loss to obtain radiating surface is 0.69. 
This is practically 3.00 times that for direct heating. 



CUBIC FEET OF AIR PER HEAT-UNIT FROM WALL PER 

DEGREE DIFFERENXE. 



T-t. 



t. 



60* 



70^ 



T-L 



t. 



6o< 



10 
20 

30 
40 

50 



337 


1 

400 


172 


204 


116 


138 


84 


106 


72 


86 



60 
70 
80 
90 

100 



61 

53 
48 

43 
39 



70' 



73 
63 
57 
51 
47 



T =tcmp. of entering air. / —temp, of room. 

The above table gives the number of cubic feet of air 
required per hour in indirect heating to maintain the proper 
temperature, as computed by formulae (4), for each heat-unit 
lost from walls and windows of room for a temperature of 60*^ 
or 70° above outside air. The total air required will be found 
by multiplying the values, as given in the table, by the total 
heat lost per degree difference of temperature from the room. 



266 HEATING AND VENTILATING. 

This loss is designated by H in formulae (4), and is approxi- 
mately equal to the glass plus J the exposed wall surface 
expressed in square feet. 

Thus to find the number of cubic feet of air required to 
warm a room to 70° in zero weather, for G+\w ^128 and 
r— /=3o; multiply 138 from table by 128. 

For indirect heating, 50 per cent more surface is usually allowed 
than for direct, although some engineers add only 25 per cent. 

The heat given off from indirect heating surfaces would 
seem from experiments to depend largely upon construction. 
If surfaces are crowded the heat transfer will be small. If the 
entire surface of extended surface radiators is figured as effective 
the coefficient should be reduced about 10 per cent. For 
forced draft the coefficient may be taken as 4 to 6 or about 
100 per cent greater than natural circulation. 

115. Summary of Approximate Rules for Estimating Radiating 
Surface. — Some very simple rules may be given for heating to 
70° in zero weather: 

First. The amoimt of heat required to supply that lost 
from the room per degree difference of temperature is approx- 
imately equal to the area of the glass in square feet plus J the exposed 
wall surface. 

Second. The heat necessary to supply loss from ventila- 
tion for dwelling houses, first floor, is 0.04 of the cubic contents 
per hour for living-rooms; 

0.06 of the cubic contents for halls; 

0.02 of the cubic contents. for upper stories. 

For churches, auditoriums, the loss to supply ventilation 
should be taken as 0.005 to 0.0 1 of the cubic contents; for offices, 
banks, etc., 0.02 to 0.04 of the cubic contents, depending upon 
circumstances. 

Note. — 1/50=0.02 is substituted here for 1/55 used in previous cal- 
culations. The error thus made in result is less than one-tenth of one 
per cent and is negligible. 

Third. To find the radiating surface for direct steam-heat- 
ing, multiply the sum of the numbers as given by rules First 
and Second by J. 



GRAVITY STEAM-HEATING SYSTEMS. 267 

Fourth. To obtain the radiating surface for direct hot- 
water heating, multiply the sum of the numbers as given by 
rules First and Second by 0.4 to 0.42. It should be noted that 
from 60 to 67 per cent more radiating surface is required for 
hot- water than for steam-heating, consequently it becomes 
p>ossible to compute radiating surface for both methods of heat- 
ing by one rule, viz., that for steam-heating, by multiplying for 
hot-water heating by the proper factor. 

When the minimum temperature is 10 degrees below zero 
Fahr., the radiating surface should be increased by 5 per cent, 
when 20 degrees below zero by 10 per cent, etc. 

For indirect heating the following rules will give quite sat- 
isfactory results when the temperature of the room is to be 
maintained at 70° with outside air at zero and the heated air 
brought in at a temperature 30° above that in the room. In 
this calculation the surface of the steam radiator is supposed 
to be 212°, that of the hot- water radiator 170° Fahr. The 
coefficients are taken from the preceding table. 

Rule. — The radiating surface for indirect heating is equal 
to the glass surface plus one-fourth the exposed wall surface 
in square feet multiplied by the following factors: 

Steam-heating. Hot-water Heating. 

I St Story 0.7 1.15 

2d * * 0.6 I . o 

3d ** 0.5 0.8 

The total amount of air supplied will be given by the fol- 
lowing: 

Rule. — The air in cubic feet per hour is found by multi- 
plying the radiating surface, computed as in above rule, by the 
following factors : 

Steam-heating. Hot-water Heating. 

ist Story 200 150 

2d ** 170 130 

3d " 150 IIS 

If this is insufficient for ventilating purposes more air must 
be introduced, which must be heated to 70° F., and this will 
require an additional foot of surface for each additional 300 
cubic feet of air heated by steam, and for each additional 200 
cubic feet heated by hot water. 



268 HEATING AND VENTILATING. 

Rule for area of hot-air duct in indirect heating: 
The cross-sectional area of the hot-air duct leading from 
the indirect heating surface or radiator to the room to be warmed 
should be as follows for each square foot of surface in the 
radiator : 

Steam«heating. Hot-water Heating. 

For the first story, square inches 1.5 1.8 

** second story ** .... i.o 1.25 

** third story ** 0.9 i.i 

Make area cold-air flue 75 to 80 per cent of that of the hot- 
air flue. 

116. Computation of Steam-piping. — An approximate method 
of computing the size of pipes required for steam-heating 
would be as follows: First find the amount of steam by divid- 
ing the total number of heat-units given out by i square foot 
of radiating surface by the latent heat in i pound of steam, 
this will give the weight of steam required per square foot; 
this multiplied by the number of cubic feet in i pound of steam 
will give the volume which will be required for each square 
foot of radiating surface. Knowing this quantity the size 
of pipe may be computed from the considerations already 
given, either by formulae or by assuming the velocity of flow 
as equal that due to the head, corrected for friction; 25 to 50 
feet per second can in nearly every case be realized. As an 
illustration; compute the size of main steam-pipe required to 
supply 1000 feet of radiating surface with steam at a temper- 
ature of 212 degrees when the surrounding temperature of the 
air is 70: For this case i square foot of radiating surface can 
be assumed ordinarily as giving off (1.8 times 142) 255 heat- 
units. To supply 1000 feet of surface 255,000 heat-units per 
hour would be required; as each pound of steam during con- 
densation will give up 966 heat-units, we will need for this 
purpose 264 pounds per hour; and as each pound of steam 
at this temperature makes 26.4 cubic feet, we will require 6970 
cubic feet of steam per hour, or 1.94 cubic feet per second. 

If we proportion the pipes so that the velocity shall not 
exceed 25 feet per second, the area of the pipe must be 0.077 
square foot, which equals ii.i square inches. For this we 



GRAVITY STEAM-HEATING SYSTEMS. 



269 



would require a pipe 4 inches in diameter. K we had assumed 
the velocity to be 50 feet per second, the area would have 
been 5.6 square inches and the diameter 3 inches; if we had 
assumed a velocity of 100 feet per second, the area required 
would have been 2.8 square inches and the diameter of the 
pipe required would have been somewhat less than 2 inches. 
The friction in a pipe when steam is moving at a velocity of 
100 feet per second causes a reduction in pressure of about i^ 
pounds in 100 feet, a velocity of 50 feet per second causes 
about J as much, and a velocity of 25 feet about tt as much. 
Indirect surfaces of the same extent usually require twice as 
much steam and a pipe with area twice as great as that needed 
for direct radiation. 

For the single-pipe system of heating an additional amount 
of space must be provided in the steam main to permit the 
return of the water of condensation. The actual space occupied 
Jby the water is small compared with that taken by the steam, 
but in order to afford room for the free flow of the currents 
of water and steam in opposite directions, experience indicates 
that about 50 per cent more area should be provided than is 
required in the separate return or double pipe system of heat- 
ing. 

By similar computations we obtain the following factors, 
which are to be multiplied by the radiating surface to obtain 
areas and diameters of steam-heating mains in inches: 

APPROXIMATE AREA AND DIAMETER OF STEAM-MAIN. 



Velocity of 

Steam. Pt. 

per Sec. 

(I) 


Multiply each lOO Sq. Ft. 
Radiating Surface tor 
Area Steam Main by 

(2) 


Multiply Sq. Root Radi- 
ating: Surface for 
Diameter by 

(3) 


Probable 

Frictional 

Resistance 

per 100 Ft., 

Ins. Water. 

(4) 


Required 

Steam 

Pressures. 

Lbs. 

is) 




Double-pipe 
system. 


Single-pipe 
system. 


Double-pipe 
system. 


Single-pipe 
system. 






25 


.90 


I 35 


.107 


.131 


2.0 


to I 


37.5 


.675 


I.OI 


.092 


•"3 


6.0 


2 to 3 


SO 


.45 


0.67 


.075 


.092 


8.0 


3 to 4 


62.5 


375 


0.56 


.069 


.090 


12.6 


4 to 5 


75 


.30 


0.4s 


.062 


.075 


18.0 


5 to 6 


100 


.225 


0.34 


.054 


.066 


32.0 


6 to 40 



In all cases if the mains are not covered, its surface is to be estimated as a part of the 
radiating surface. 



270 HEATING AND VENTILATING. 

The preceding table gives in the first column the velocity of 
steam, in the second column the corresponding area of pipe 
in square inches required for each loo square feet of radiating 
surface for the double and single pipe systems of heating, in 
the third column the diameter of pipe for each square foot of 
radiating surface for both systems of heating, which latter 
is to be multiplied by the square root of the given radiating 
surface, to obtain the diameter required. Colunm 4 gives the 
approximate back pressure in inches of water per 100 feet in 
length of the main for steam having the same velocity as in 
column I. Column 5 suggests steam-pressures which will 
render any of these values satisfactory in practice. 

117. Rules for Steam-pipe Sizes. — Most of the rules which 
have been given for determining sizes of steam-pipe when the 
radiating surface only is given will be found included in the 
tabulated values. Thus Mr. George H. Babcock gives a 
rule for gravity heating-systems with separate returns as fol- 
lows:* " The diameter of the mains leading from the boiler 
to the radiating surface should be equal in inches to one-tenth 
the square root of radiating surface, mains included, in square 
feet." By consulting the table already given, column 3, this 
factor would corresp>ond to a velocity of steam slightly exceed- 
ing 25 feet per second, and would be adapted for low-pressure 
steam-heating in small plants. 

One authority f gives the following rules for determining 
the cross-sections of area of pipes: " For steam-mains and 
returns it will be ample to allow a constant of 0.375 of a square 
inch for each 100 square feet of heating surface in coils and 
radiators, 0.375 ^^ ^ square inch when exhaust steam is used, 
0.19 of a square inch when live steam is used, and 0.09 of a square 
inch for the return. Steam-mains should never be less than 
1 5 inches, nor the returns less than three- fourths of an inch, in 
diameter." Mr. Alfred R. Wolff uses a table for obtaining 
the capacity of steam-mains of a given diameter, the capacity 
being expressed both in heat-units delivered and in radiating 

* Transactions American Society Mechanical Engineers, May, 1885. 
t Van Nostrand's Science Series, No. 68. 



GRAVITY STEAM-HEATING SYSTEMS. 



271 



surface. This table is given on the next page and will be 
found convenient and accurate. 

The size of main steam-pipe depends on the consideration 
already given; the smaller the size the greater the resistance 
of the steam and the more friction and consequent back pressure 
on the system; the larger the pipes that are used the less the 
resistance, and, in general, the more satisfactory the results, 
but economy, of course, forbids the use of pipes beyond a cer- 
tain size, and that size should be selected by considerations 
relating to pressure, velocity of steam, and friction, as explained. 



TABLE FOR THE CAPACITY OF STEAM-PIPES 100 FEET IN LENGTH 

WITH SEPARATE RETURNS. 







By A. R. Wolff. 










2 Lbs. Pressure. 


5 Lbs. Pressure. 


Diameter 


Diameter 

of Return. 

Inches. 










of Supply. 
Inches. 


Total Heat 

Transmitted. 

B.T.U. 


Radiating 

Surface. 

Square Feet. 


Total Heat 

Transmitted. 

B.T.U. 


Radiating 

Surface. 

Square Feet. 


I 


I 


9,ooo 


36 


15,000 


60 


li 


I- 


i8,ooo 


72 


30,000 


120 


ij 


li 


30,000 


120 


50,000 


200 


2 


li 


70,000 


280 


120,000 


480 


2j 


2 


132,000 


528 


220,000 


880 


3 


2i 


225,000 


900 


375,000 


1,500 


3J 


2} 


330,000 


1,320 


550,000 


2,200 


4 


3 


480,000 


1,920 


800,000 


3,200 


4i 


3 


690,000 


2,760 


1,150,000 


4,600 


5 


3i 


930,000 


3J20 


1,550,000 


6,200. 


6 


3i 


1,500,000 


6,000 


2,500,000 


10,000 


7 


4 


2,250,000 


9,000 


3,750,000 


15,000 


8 


4 


3,200,000 


12,800 


5,400,000 


21,600 


9 


4i 


4,450,000 


17,800 


7,500,000 


30,000 


lO 


5 


5,800,000 


23,200 


9,750,000 


39.000 


12 


6 


9,250,000 


37.000 


15,500,000 


62,000 


14 


7 


13,500,000 


S4,ooo 


23,000,000 


92,000 


i6 


8 


19,000,000 


76,000 


32,500,000 


130,000 



In above table each square foot of radiating surface is 
assumed to transmit 250 heat-units per hour, a safe and con- 
servative estimate, as will be seen by consulting Chapter IV. 

For pipes of greater length than 100 feet multiply results 



272 HEATING AND VENTILATING. 

in the above table by the square root of loo divided by the 
length. In all cases the length is to be taken as the equivalent 
length in straight pipe of the pipe, elbows, and valves.* For 
other lengths multiply above results by following factors: 

I«ength of pipe in feet . . 200 300 400 500 600 700 800 900 1000 
Factor 0.71 0.58 0.5 0.45 0.41 0.38 0.35 0.33 0.32 

For example, the capacity of a pipe 8 inches in diameter 
and 800 feet long would be 0.35 of 12^800 sq. ft. of radiating 
surface = 4480 sq. ft. It will be noted that the size of return 
specified by Mr. Wolff is about one pipe-size greater than 
believed to be necessary by the author. 

Unless otherwise impracticable the author would always 
advise the use of the table of commercial sizes of steam-mains 
in proportioning pipe sizes. In using the table, first find the 
size of the branch pipes from single radiators, and then the 
size of the mains which will be increased with amount of 
radiation carried, as shown in the table. 

118. Size of Return-pipes, Steam-heating. — ^The size of 
return-pipes, if figured from the actual volume of water to 
be carried back, would be smaller than is safe to use, largely 
because of air which is contained in the steam-pipes, and which 
does not change in volume when the steam is condensed. For 
this reason it is necessary to use dimensions which have been 
proved by practical experience to be satisfactory. WTien the 
steam-main is large, the diameter of the return-pipe will prove 
satisfactory if taken one size less than one -half that of the 
steam-pipe; but if the steam-main is small, for instance, 5 
inches or less, the return-pipe should be but one or two sizes 
smaller. The return-pipe should never be less than i inch, in 
order to give satisfactory results. The following table suggests 

* XoTE. — In case there are bends or obstructions consider the length of pipe 
increased as follows: Right-angle elbow 40 diameters; globe-valve 125 diameters; 
entrance to tee 60 diameters. 

For obtaining the diameter of steam-main to be used in case there is a separate 
return multiply the above results by 0.82. 

For indirect heating without separate return multiply above results by 1.4, 
with separate return use the results in the form given. 



GRAVITY STEAM-HEATING SYSTEMS. 



273 



sizes of returns which will prove satisfactory for sizes of main 
steam-pipes as given: 



Diameter 


Diameter 


Diameter 


Diameter 


Steam-pipe. 


Return-pipe. 


Steam-pipe. 


Return-pipe. 


• 

inches. 


inches. 


inches. 


inches. 


li 


li 


S 


3 


2 


li 


6 


3i 


2i 


li 


8 


4 


3 


2 


9 


4i 


3i 


2i 


lO 


4} 


4 


»i 


12 


S 



The size of return-pipes, if computed on basis of reduc- 
tion in volume due to condensation of the steam, supp>osing 
the steam to have a gauge-pressure of 40 pounds and that one- 
half its volume is air, would be, neglecting friction, about one- 
sixth of that of the main steam-pipe, which is much smaller 
than would be considered safe in practice. 

Main and Return-pipes for Indirect Heating Surfaces. — ^The 
indirect heating surfaces require about twice as much heat as 
the same quantity of direct radiating surface, and hence, for 
same resistance in the pipe, the area should be twice that 
required in direct heating. It will usually be sufficiently 
accurate to use a pipe whose diameter is 1.4 times greater than 
that for direct heating. 

Reliefs and Drip-pipes. — ^The size of drip-pipes necessary 
to convey the water of condensation from a steam main to a 
return cannot be obtained by computation, as there is much 
uncertainty regarding the amount of water that will flow 
through, under the conditions which exist. 

As. the flow through the relief tends to increase the pres- 
sure in the return, it may also serve to lessen the velocity of 
flow beyond the point of junction, provided the size is greater 
than necessary to carry off the water of condensation from the 
steam-main. Drip-pipes should be united to the return in 
such a manner as to re-enforce rather than impede the circula- 
tion, which result can usually be attained by joining the pipes 
with 60 or 45 degree fittings. 



274 



HEATING AND VENTILATING. 



The writer would recommend the employment of the fol- 
lowing sizes of drip-pipes as ample for usual conditions: 

DIAMETER OF DRIP-PIPE FOR STE.VAI-MAINS OF VARIOUS 

LENGTHS. 



Diameter 

of 

Steatn-main. 

Inches. 



Length of Steam-main in Feet. 



o to lOO. 



lOO to 200. 



200 to 400. 



400 to 600. 



Diameter of Drip-pipe in Inches. 



OtO 2 

3 
4 

5 
6 



1 


i 


i 


i 


i 


} 


1 
« 


I 


i 


} 


I 


li 


« 


I 


li 


li 


I 


li 


li 


li 



119. Summary of Various Methods of Computing Quan- 
tities Required for Heating. — The following table gives the 
required size of steam-pipes and of steam-boiler or hot-water 
heater, for various amounts of radiating surface. The propor- 
tions given will apply to residence heating or where the length 
of main pipe is not over 200 feet. The value given for the 
steam-main is that for the single-pipe system when no return 
is needed. For the system of separate steam- and return- 
pipes the diameter of the steam-main should be taken J of 
that given. The cubic space heated is given if the ratio to 
radiating surface be known; this is an approximation only, 
althoijgh it may often serve a useful purpose when experience 
has been gained of heat required in constructions of similar 
nature in the same locality. 

About two -thirds as much air is warmed by hot- water as 
by steam radiators, and flues should be about two -thirds as 
large as given in the table on page 276. 



GRAVITY STEAM-HEATING SYSTEMS. 



275 





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276 HEATING AXD \'ENTILATING. 

HOT-AIR AXD XXXTILATIXG FLUES. 
IxDiKECT Radiation Steam CacuLAnox. 



Square feet 

Cubic feet air per minute 

Area hot-air flue, square feet: 



25 so 75 100 125 150 175 200. 350 
122 244 362 486 602 729 846 972 1220 

I 

iststocy 0.721.45^162.8735743 50 57,7.3 

ad story 0.290.590.88 19 1.47 1.78 2.06 2.35I2.9S 

3d story 0.240.490.730.971.22 1. 461. 7 i.95'2.45 

Area ventilating flue, square feet: i 

I St story 0.370. 741. 1 1. 461. 81 2.2 2.572.953.7 

2d Story 0.480.87 1.44 1.92 2.37 2.8 3.353.844.8 

3d Story 0.551. 1 1.642.2 2.71 $.i 3-854.4 5.4 

Actual area register, square feet: I • I I 

iststory ;i.222.4 3.6 49 6 7.3 8.4 9-7 '12.2 

2d and above i.o ;2 3 4 5 67 '8.0 '10.0 

Ventilating register, square feet. . .0.6 '1.2 1.8 2.4 3 3.6 4.2 4.8 6.1 



120. Short Method of Ccmqioting Radiatkm, published by 
A. C. Rogers in the Heating and Ventilating Magazine. Tables 
for the radiating surface for hot water and for steam are given 
on the following pages. It will readily be seen that by taking 
oflF from the drawings the quantities for each of wall, glass and 
cubic contents, the radiation for which is readily found from 
the tables, and by adding these values, the radiation sought is 
the result of this sum. First, get the value of radiating surface 
needed for each item for the room and then their sum equals 
the radiating surface required for that room. For instance, if 
a room had 100 square feet of wall surface it would require 10 
square feet of radiating surface, with 10 square feet of window 
siirface would require 4 square feet of radiating surface, and 
with a cubic content of 2000 cubic feet, and 2 changes of air 
per hour would require ^2 square feet of radiating surface; 
or a total of 46 square feet of radiating surface for the room. 

The table for hot water is computed for the formula. 



/e = o.4("--^G>o.o2 Sc\ 



GRAVITY STEAM-HEATING SYSTEMS. 277 

where R = the radiating surface in square feet, 

W= '' waU 

G= '' glass 

C = ' * contents of the room in cubic feet, 

iV= '* number of times per hour the air is changed. 
The table for steam is computed from the formula, 



/W \ 

i2=o.25f — hG+o.o2 NCj. 



Time may be saved by properly tabulating the values of 
the items taken from the drawings and by the use of an adding 
machine. 



278 



HEATING AND VENTILATING. 



SQUARE FEET OF RADIATION FOR HOT WATER. 



^% A.* A. 


Square Feet Surface. 


Cubic Feet of Air Contents 


1. 


Quantity. 
















Wall. 


Glass. 


N-i. 


N-2. 


N=3. 


N-4. 


I 


.1 


.4 


.008 


.016 


.024 


032 


2 


.2 


.8 


.016 


.032 


.048 


.064 


3 


.3 


1.2 


.024 


.048 


.072 


.096 


4 


.4 


1.6 


.032 


.064 


.096 


.128 


S 


S 


2.0 


.040 


.080 


.120 


.160 


6 


.6 


2.4 


.048 


.096 


.144 


.192 


7 


.7 


2.8 


.056 


.112 


.168 


.224 


8 


.8 


3-2 


.064 


.128 


.192 


.256 


9 


.9 


3-6 


.072 


.144 


.216 


.288 


lO 


I.O 


4.0 


.080 


.160 


.240 


.320 


20 


2.0 


8.0 


.160 


.320 


.480 


.640 


30 


. .0 


12.0 


.240 


.480 


.720 


.960 


40 


4.0 


16.0 


.320 


.640 


.960 


1.280 


SO 


50 


20.0 


.400 


.800 


1 .200 


1 I .600 


60 


6.0 


24.0 


.480 


.960 


1.440 


1.920 


70 


7.0 


28.0 


.560 


1 . 120 


1.680 


2 . 240 


80 


8.0 


32.0 


.640 


1.280 


1 .920 


2.560 


90 


9.0 


36.0 


.720 


1.440 


2.160 


! 2.880 


100 


10. 


40.0 


.800 


1.600 


2.400 


3.200 


2cx:> 


20.0 


80.0 


1 .600 


3.200 


4.800 


6.400 


300 


30.0 


120.0 


2.400 


4.800 


7.:;oo 


9.600 


400 


40.0 


160.0 


3.200 


6.400 


0.()OO 


12.800 


500 


50.0 


200.0 


4.000 


8.000 


12.000 


16.000 


600 


60.0 


240.0 


4.800 


9.600 


14.400 


10 200 


7cx> 


70.0 


280.0 


5.600 


II . 200 


16 800 


22.000 


800 


80.0 


320.0 


6.400 


12.800 


IQ.200 


25.600 


900 


90.0 


360.0 


7.200 


14.400 


2 1 . 600 


28.800 


I,OCX> 


lOO.O 


400.0 


8.000 


16.000 


24.000 


32.000 


2,000 


200.0 


800.0 


16.000 


32.000 


48.000 


' 64.000 


3,000 


300.0 


1,200.0 


24.000 


48.000 


72.000 


Q6.000 


4,000 


400.0 


1,600 


32.000 


64.000 


96 000 


128.000 


S,ooo 


500.0 


2,000.0 


46.000 


80.000 


120.000 


160.000 


6,000 


600.0 


2,400.0 


48. 000 


96.000 


144 .000 


192.000 


7,000 


700.0 


2,800 


, 56 . 000 


112.000 


I 08 000 


224.000 


8,000 


800.0 


3.200.0 


64.000 


128.000 


192.000 


256.000 


9,000 


900.0 


3,600.0 


1 72.000 


144.000 


216.000 


; 288.000 


10,000 


1000. 


4,000.0 


80.000 


160.000 


240.000 


320.000 


20,000 


2000.0 


8,000.0 


' I()0.000 


320.000 


480.000 


' 640 . 000 


30,000 


3000.0 


12,000.0 


240.000 


480.000 


720.000 


960.000 


40,000 


4000.0 


16,000.0 


1 ?20.000 


640 . 000 


Qr>0.000 


1280.000 


50,000 


5000.0 


20,000 . 


1 400.000 


800.000 


1220.000 

1 


1600.000 


60,000 • 


6000.0 


24,000.0 


480.000 


960.000 


1444.000 


1920.000 


70,000 


7000.0 


28,000.0 


560.000 


1 1 20 . 000 


1680.000 


2240.000 


80,000 


8000.0 


32,000.0 


640.000 


1280.000 


1920.000 


2560.000 


90,000 


9000.0 


36,000.0 


720.000 


1440.000 


2160.000 


2880.000 


100,000 


lOOOO.O 


40,000 . 


800.000 


1600.000 


2400.000 


3200.000 



GRAVITY STEAM-HEATING SYSTEMS. 



279 





SQUARE 


FEET OF RADIATION FOR 


STEAM. 




^\ A.* A. 


Square Feet Surface. 


Cubic Feet of Air Contents 


• 


Quantity. 
















Wall. 


Glass. 


N-i. 


N=2. 


N=3. 


N-4. 


I 


0.0625 


.25 


0.005 


O.OIO 


0.015 


0.020 


2 


.1250 


.50 


O.OIO 


0.020 


0.030 


0.040 


3 


.1875 


.75 


0.015 


0.030 


0.045 


0.060 


4 


.2500 


1. 00 


0.020 


0.040 


0.060 


0.080 


5 


•3125 


1.25 


0.025 


0.050 


0.07s 


o.ioo 


6 


•3750 


1.50 


0.030 


0.060 


0.090 


0.120 


7 


.4375 


I 75 


0.035 


0.070 


0.105 


0.140 


8 


.5000 


2.00 


0.040 


0.080 


0.120 


0.160 


9 


-5625 


2.25 


0.045 


0.090 


0.135 


0.180 


lO 


0.625 


2.50 


0.05 


O.IO 


o.iS 


0.20 


20 


1.250 


5.00 


O.IO 


0.20 


0.30 


0.40 


30 


1.875 


7.50 


0.15 


0.30 


0.45 


0.60 


40 


2.500 


10.00 


0.20 


0.40 


0.60 


0.80 


50 


3125 


12.50 


0.25 


0.50 


0.75 


1. 00 


60 


3 750 


15.00 


0.30 


0.60 


0.90 


1.20 


70 


4 375 


17.50 


0.35 


0.70 


I. OS 


1.40 


80 


5.000 


20.00 


o*.40 


0.80 


1.20 


1.60 


90 


5625 


22.50 


0.45 


0.90 


1.3s 


1.80 


100 


6.25 


25.0 


05 


1.0 


I 5 


2.0 


200 


12.50 


50.0 


I.O 


2.0 


3.0 


4.0 


300 


18.75 


75 


1-5 


30 


45 


6.0 


400 


25.00 


100. 


2.0 


4.0 


6.0 


8.0 


500 


31 25 


125.0 


2-5 


so 


7-5 


10. 


600 


37 50 


150.0 


30 


6.0 


9.0 


12.0 


700 


43-75 


175 


3-5 


7.0 


10.5 


14.0 


800 


50.00 


200.0 


4.0 


8.0 


12.0 


16.0 


900 


56.25 


225.0 


4.5 


9.0 


13.5 


18.0 


I,CXX> 


62. 5 


250.0 


5.0 


10. 


150 


20.0 


2,000 


125.0 


500.0 


10. 


20.0 


30.0 


40.0 


3,000 


187.5 


750.0 


15 


30.0 


45-0 


60.0 


4,000 


250.0 


1,000.0 


20.0 


40.0 


60.0 


80.0 


S,ooo 


312.5 


1,250.0 


25.0 


50.0 


75.0 


100. 


6,000 


3750 


1,500.0 


30.0 


60.0 


90.0 


120.0 


7,000 


437-5 


1,750 


35-0 


70.0 


105.0 


140.0 


8,000 


500.0 


2,000.0 


40.0 


80.0 


120.0 


160.0 


9,000 


562.5 


2,250.0 


45.0 


90.0 


135.0 


180.0 


10,000 


625.0 


2,500.0 


50.0 


100. 


150.0 


200.0 


20,000 


1250.0 


5,000.0 


100. 


200.0 


300.0 


400.0 


30,000 


1875.0 


7,500.0 


150.0 


300.0 


450.0 


600.0 


40,000 


2500.0 


10,000.0 


200.0 


400.0 


600.0 


800.0 


50,000 


3125.0 


12,500.0 


250.0 


500.0 


750.0 


1000. 


60,000 


3750.0 


15,000.0 


300.0 


600.0 


900.0 


1200.0 


70,000 


4375-0 


17,500.0 


350.0 


700.0 


1050.0 


1400.0 


80,000 


5000.0 


20,000 . 


400.0 


800.0 


1200.0 


1600.0 


90,000 


5625.0 


22,500.0 


450.0 


900.0 


1350.0 


1800.0 


100,000 


6250.0 


25,000.0 


500.0 


1000. 


1500.0 


2000.0 



CHAPTER XI. 
PUMP RETURN STEAM HEATING SYSTEMS. 

130. General Remarks. — Under this heading will be taken 
up, under their various trade names, the diflferent systems of 
Vacuum, Vapor or Atmospheric steam heating, in which the 
water is returned to the boiler by a pump or injector, etc., or 
else wasted; as well as high pressure steam heating, whether 
the steam is furnished directly from the boiler or indirectly 
by using the exhaust steam of engines, turbines, pumps, etc. 
Steam after being employed in an engine contains the greater 
p>ortion of its heat, and if not condensed or utilized for other 
purposes it can usually be employed for heating without mate- 
rially affecting the p>ower of the engine. The systems of steam- 
heating which have been described are those in which the water 
of condensation flows directly into the boiler by gravity. In 
other systems in use high-pressure steam is carried in the boilers, 
high- or low-pressure steam in the heating-mains and radiators, 
and the return-water of condensation is received by a trap 
and delivered either into a tank from which it is pumped 
into the boiler or in some instances wasted. The exhaust 
steam may need to be supplemented by live steam taken directly 
from the boiler, which may be reduced in pressure either by 
passing through a valve partly open or a redudng-valve. 

It will often be found that little attempt is made to utilize 
the heat escaping in the exhaust steam from non-condensing 
engines, and consequently a good opportunity exists for con- 
struction of systems which will save annually many times 

their first cost. 

280 



PUMP RETURN STEAM HEATING SYSTEMS. 281 

131. Systems of Exhaust Heating. — ^The exhaust steam 
discharged from non-condensing engines contains from 20 
to 30 per cent of water, and considerable oil or greasy matter 
which has been employed in lubricating. When the engine 
is freely exhausting into the air, the pressure in the exhaust- 
pipe is, or should be, but slightly in excess of that due to the 
atmosphere. The effect of passing exhaust steam through 
heating-pipes is likely to increase the resistance and cause back 
pressure which will reduce the effective work of the engine. 
The engine delivers steam discontinuously, but at regular 
intervals at the end of each stroke. The amount is likely 
to vary with the work done by the engine, since the engine- 
governor is always adjusted to admit steam in such amoimt 
as is required to preserve uniform speed; if the work is light 
very little steam will be admitted to the engine. For this reason 
the supply available for heating varies within wide limits. 

The general requirements for a successful system of exhaust- 
steam heating must be, first, the arrangement of a system of 
piping having such proportions as will make little or no 
increase in back pressure on the engine and will provide for 
using an intermittent supply of steam; second, provision for 
removing the oil from the exhaust, since this will interfere 
materially with the heating capacity of the radiating surfaces; 
third, provision against accidents by use of a safety or back- 
pressure valve so arranged as to prevent damage to the engine 
by sudden increase in back pressure. 

These requirements can be met in various ways. To pre- 
vent sudden change in back pressure due to irregular supply of 
steam the exhaust-pipe from the engine should be carried 
directly to a closed tank whose cubic contents should be at 
least 30 times that of the engine and as much larger as practi- 
cable. This tank can be provided with diaphragms or baffle- 
plates arranged so as to throw all or nearly all the grease and 
oil in the steam into a drip-pipe, from which it is removed by 
means of a steam-trap. These requirements are fully met by 
modem types of open feed-water heaters. To this tank may 
be connected a relief-pipe leading to the back-pressure valve, 



282 HEATING AND VENTILATING. 

and also a supplementary pipe for supplying live steam. The 
supply of steam for heating should be drawn from the top 
of the tank. 

Small sized steam turbine units usually require more steam 
than high grade steam engines of the same capacities when 
operated non-condensing or exhausting against a back pressure. 
However, the exhaust steam from turbines is free from oil or 
grease. Unless the demand for power is relatively high as 
compared with the heating load, a highly efficient steam engine 
may not show any saving at the coal pile over an engine which 
requires more steam per horse-power hour, since more live 
steam would have to be supplied to the heating system through 
a reducing valve. So each installation is a separate problem, 
its most economical solution depending upon the average 
amount and distribution of the power and heating loads as 
well as other commercial conditions. 

Any system of piping may be adopted, but extreme care 
should be taken that as little resistance as possible is intro- 
duced at bends or fittings. The radiating surface employed 
should be such as will give the freest possible circulation. 
In general, that system will be preferable in which the main 
steam-pipe is carried directly to the top of the building, the 
distributing-pipes run from that point, and the radiating sur- 
face is supplied by the down-flowing current of steam. It is 
desirable to have a closed tank at the highest point of the sys- 
tem, from which the distributing-pipes are taken, and provided 
with drips leading to a trap so as to remove, before it can reach 
the radiating surface, any water of condensation or oil which 
has been carried to the top of the building. 

132. Proportions of Radiating Surface and Main Pipes 
Required in Exhaust Heating. — The size of exhaust pip)e 
required for an engine of given power, in order that the back 
pressure shall not exceed a certain amount, may be computed, 
the only data required in addition to that already given for 
heating with live steam being that relating to the steam 
required by engines. The amount of steam used by engines 
will depend upon the workmanship and class to which they 



PUMP RETURN STEAM HEATING SYSTEMS. 



283 



belong, but we can assume with little error that non-con- 
densing engines will require the following weights of steam per 
horse-power per hour: simple with throttling-govemor 40 
pounds, with automatic governor 35 pounds, with Corliss valves 
30 pounds, compound using high-pressure steam 25 pounds. 
In order that the pipes may be suflSciently large it is better to 
proportion the systems for the more uneconomical type. 

TABLE OF DATA FOR COMPUTATION. 



Steam -pressure from Atmosphere. 
Absolute 



Temperature of steam. F 

Temperature of air 

Difference 

Heat per min. from lOO sq. ft. radiation 

in B.T.U. equal 3 times difference 

Total heat of steam above 21 a'* 

Latent heat steam. B.T.U 

Cubic feet steam per lb 

Cubic feet steam to wei^h f lb 

Cubic feet steam required each min. to 

supply 100 ft. rad. sur.. air 70°. . . 

Weight of I cubic foot steam lbs. 

ThrottlinK 
Radiating surface per 

H.P 



Head of steam in feet equal 
of water column. . . . 



Automatic 

Corliss . . . , 

Compound 

I foot water 



212 

70 

142 

426 

966 

966 

26.4 

17.6 

II. 6 

0370 

IS2 

134 

114 

95 

1669 



I 


2 


3 


10 


IS. 7 


16.7 


18.7 


24- 7 


216 


219 


222 


239 


70 


70 


70 


70 


146 


149 


152 


169 


438 


447 
967 


456 


507 


967 


967 


973 


963 


960 


957 


946 


24.6 


23.3 


21.0 


16.2 


16.4 


IS. 5 


14.0 


10.8 


II. 25 


10. 8s 


10. I 


8.8 


.0403 


.0427 


.0475 


.0640 


146 


143 


139 


126 


129 


127 


122 


112 


no' 


107 


104 


95 


91 


90 


87 


79 


1585 


1455 


I317 


lOIO 



I 



— 2 I 
12.7 

204 1 
70| 

134I 

402 

962 

970 

30.3 

20.2 

12.6 

.0326 
162 
146 

123 
102 

1902 



-5 

9.7 

192 

70 

122 

366 

958 

978 

30.0 

2O.O 

II. S 
.0257 
179 
158 
134 
112 

2440 



In the following discussion the dimensions of piping are 
computed for an engine using 40 pounds of steam per horse- 
power per hour (| pound per minute), and exhausting against 
a back pressure above or below atmosphere as stated.* The 
preceding table gives properties of steam, also radiating sur- 
face supplied per^ horse-power by engines of various classes. 

The computation of the size of exhaust-pipes can be made by the 
following algebraic process: 

Let V equal velocity of the steam in feet per second; F, velocity in 
feet per minute; /, length of pipe in feet; D, diameter of pipe in feet; 
dj diameter in inches; A, area of pipe in square feet; Q, cubic feet of 
steam discharged per minute; A, back pressure above atmosphere expressed 
in feet of steam; p, back pressure expressed in pounds per square inch; 
HP, horse-power of engine; c, number of cubic feet in one pound of 
steam. 



* Radiating surface 25 per cent less. 



284 HEATING AND VENTILATING. 

From the following formulae (see Chapter V), we have, for velocity in 
feet per second 

from which by reduction the velocity in feet per minute 



,^fD=866^f 



V=30ooxhD=S66x-d (2) 



The discharge in cubic feet per minute 



Q=AV=^SOooAyjjD=4'723yJjd' (3) 

Since i pound of steam is used per horse-power per minute, 

Q=lcHP (4) 

From above by reduction 

^=o.537-y/-^ = o.457^y^/' J (5) 



HP^r-^r^y^^ (6) 



In case the back pressure is equal to one foot of water column (0.433 
pound per square inch) above atmosphere, //=i5o8, c=2$.y, and we 
have 

//P=i.iiV^. 

For one pound back pressure 

IIP=i.iS\ (K 

It is advisable to make the diameter one inch greater to 
overcome additional resistances. (See table.) 



PUMP RETURN STEAM HEATING SYSTEMS. 



285 



RADIATING SURFACE AND HORSE-POWER OF EN'GINE FOR A 

GIVEN DIAMETER OF EXHAUST-PIPE. 



Diatn. Ex- 




haust-steam 




Pipe lOo Ft. 


Correspond- 
ing H.P. of 
Engine. 


Long. Back 


Pressure not 


to Exceed 




0.4 Lb. 




Inches. 




2 


1. 12 


2i 


3.1 


3 


6.4 


3J 


II. I 


4 


17. 5 


4l 


22.9 


5 


36.6 



Radiating Sur- 
face in Sq.ft. 
Supplied by 
Automatic 
Type of 
Engine. 



no 
300 
605 
1,050 
1,650 
2,200 
3,400 



Diam. Ex- 
haust-steam 
Pipe xoo Ft. 
Long. Back 
Pressure not 
to Exceed 
0.4 Lb. 



Correspond- 
ing H.P. of 
Engine. 



Inches. 
6 

7 

9 
12 

14 
16 

18 



63 
99. 

304 

356 
562 

82s 
1,150 



Radiating Sur- 
face in Sq.ft. 
Supplied by 
Automatic 
Type of 
Engine. 



6,200 
9,500 
19,500 
34,000 
54,000 
89,000 
110,000 



The foregoing table is computed for steam having a pressure 
of 0.43 pound above the atmosphere. For other pressures of 
exhaust multiply the results given in the table by the following 
factors (for other distances multiply by o.iVT): 



Pressure. 


Factor. 


Atmosoheric 


1.05 
1. 125 
1.27 
0.98 
0.895 

0.79 


2 pounds below 

5 pounds below 

2 pounds above 

3 pounds above 

10 pounds above 



As an example, find the size of exhaust-pipe and amount 
of radiating surface supplied by the exhaust of a 50 horse- 
power engine of the automatic type, working against a back 
pressure of 0.43 pound. For this condition, the exhaust from 
one horse-power will supply 25 per cent less than 131 square 
feet of radiation (see above table), or 4900 square feet. From 
the table at top of page we see that a 6-inch pipe will be some- 
what larger than required, but should be used. The amount 
of radiating surface needed to warm a given building will 
depend on pressure of the steam, exposure, and class of building, 
as previously explained. 



2S5 HEATI5G AXD VEynLATrXG. 

133. DBftnct Heafcms* — ^«^ pover gcoeTzted mav be all 

used in the bafLdinz or factory that c^ heated by the cxitaast 
steam: or the exhacst stejin may be nimished iroBi a separate 
establishment* usually an electric pj^rer company or a dis- 
trict heating company. 

A 2?f>xl o^mmeraal arranajement in a thicklv settled city 
fe to install a non-condensing steam tiiibtx p«^wer statixi in or 
near the centre of the heating »iistrict to be served- Then the 
tiirb«>aiteniatocs are mn in parallel with other power statioos 
whose generattag units can be nin under a high vacxnnn. the 
lijad on the non-condensing turbines in the heatrng statioa 
being S3 regulated that just the necessary- amount of exhaust 
steam is furnished to the heating system. A good com.bma- 
tii}n i*2r a smaller city k a combination electric lighting and 
power station, selling exhaust steam in the winter. :i-ni-i nqng 
the exhaust steam in the manufaccire -:■£ ice in the summer. 

The local conditions to be met ver\- Larzeiv govern the instal- 
lation and operation of 'iistrict heating plants^ Where the 
tiistances to be traasmitttfd ire great md where the buildings 
to be heated are scattered, heating by high pressure steam 
fpjm 1 'zentral station is gecerai-y used. These conditions 
are met in some educational and sta:^ institutions. Super- 
heated steam, being a poor conduct :r :c heat, is descrable 
hi the supply maL'is ru: not in ±e riciatiig surfaces. A 
mrjittriZd superhea: •:«: 5- .t :cc'' F. i: the bciler? will cut 
'ii:wzi die heat :rinsrr::ssit:n losses in :J2e ir>t :ne or two thou- 
sod reec :f rnains. 

134. Systems of Exhaust-iieaQng wich Less than Ahm^ i 
phenc Pressure. — L: i s; -f-c.-rr! .-i :\.':jusc->cd:ing discharge 
its st,ia.Ti xnc :':niien>a:i«:n ji-vcv; "i!:; -ii^; atmosphere, 
the prrissu.-.' Tiust be sig*v_'; jbc t,- •■.•»^>ri?i:r'c. but systems 
havfi betrn "i^e*: viiii -uc:v>5> n 'v?.l'1 • >c bacK :;pjssure was 
less than irTM;s:iicrj:. j:!0 'ii '.K" ' 1 ni,- .1 ;;r.[:LT*::ons which 
has b ee n z - ' t: n -u c h : .1 >*.*> .1 " v :• ; i • .^: r i.- * -.» • . 

Such X y ^C-fTi :-i:j -'*»^' x.-.'ii>i"iv.'-,.' * .- i: ro.'/jTiC -^e dis- 
chan*:; :r:m ".iit: -;^:,''T! * .* i.» i* ,\,*-r \'?.\.'i v"]! remove 
the 'va:er :i .Mici-'Msi .vi? 1 •».• » ;•*. ■ .v.." u. 1 -.tTiospheric 



PUMP RETURN STEAM HEATING SYSTEMS. 



287 



pressure; the heating surface will act as a condenser for the 
engine, and in case it is insufficient for this purpose a jet or 
surface-condenser supplied with cold water may be used to 
supplement it. Instead of an air-pump and condenser, a 
siphon condenser, Fig. 197, may be used. This latter instru- 
ment is' regularly on the market, and consists of a chamber 
above a convergent tube 
which receives the exhaust 
steam and a jet of water. 
This condenser depends for 
its action upon the fact 
that a column of water 34 
feet in height will balance 
and overcome the atmos- ,, 
pheric pressure. For its 
successful use it must be 
set so that the top of the 
condenser is at least 34 feet 
higher than the end of the 
discharge-tube, the bottom 
of which is to be sub- 
merged. 

In a system of exhaust 
heating, by-pass connec- 
tions to the outside air or 
condenser should be pro- 
vided, so that the heating 
surface need not be used in 
warm weather. 

Besides the general sys- 
tem which has been de- 
scribed, other systems of great merit have been devised and put 
on the market with many special and patented features. Of 
these we may mention first the Williames system, which is shown 
in Fig. [98, with details of construction. It will be seen that 
the exhaust from the engine is received into a large upright 
pe with back-pressure valve at top, and that the steam 




— Siphon Condenser. 



288 HEATING AND VENTILATING. 

is drawn from near the top, and after pas^g through the 
radiating system, is received into a lai^e branch-tee, which is 
supplied with injection-water and serves as a condenser. The 
suction-pipe of the air-pump is connected to the branch-tee 
and acts to remove the atmospheric pressure from the entire 




system. A by-pass for summer use is shown. Water is heated 
in the closed hot-watt-r tank by a portion of ihc return and 
may be used for any purpose ncedt'd, as. for instance, feed- 
water for boilers, heating by hot-water circulation, etc. 

The cut illustrates an automatic valve at the upper or dis- 
charge end of the exhaust-pipe, technically known as a back- 



PUMP RETURN STEAM HEATING SYSTEMS. 289 

pressure valve, which in construction is like a check-valve 
opening outward, but is provided with removable or adjust- 
able weights for the purpose of balancing any desired pressure 
inside. It is adjusted to open and discharge the steam when 
the pressure exceeds any desired amount, and to close when 
the pressure falls; it is almost universally employed to dis- 
charge the excess of steam in connection with any system of 
exhaust-heating, as already noted. When the steam supplied 
is not greater than can be condensed and removed in the form 
of water or steam by the vacuum-pump or exhausting device, a 
vacuum will be produced throughout the entire system and 
even extend to the engine; the temperature in the radiators 
will be less than the boiling-point of water and dependent 
upon the amount of vacuum. When the steam supplied is 
in excess of that which can be condensed, the back-pressure 
valve will open intermittently for a short period of time; the 
pressure in the main exhaust will be above that of the atmos- 
phere and the temperature above 212° F. The exhausting 
device will, however, for this condition, draw the steam and 
water of condensation and the entrained air through the radi- 
ators and coils and may produce considerable vacuum through- 
out the entire heating system, which may begin at a point 
near the exhaust-pipe or position of restricted supply. 

The Williames system was patented by N. P. Williames, 
April 4, 1882. It is interesting as being the fundamental 
patent granted in the United States for circulating steam 
positively without material condensation through a heating 
system by means of a suction device or exhauster connected to 
the return-pipe. 

135. The Webster System, Fig. 199, was the immediate 
successor commercially to the Williames system and is now in 
extensive use. It differs from the Williames system prin- 
cipally in the use of a thermostatic valve located in the return 
pipe from each radiator or heating coil. This valve. Fig. 200, 
is constructed on the same principle, as the automatic valve 
shown in Fig. 87, or as the expansion trap shown in Fig. 164, 
and so as to open when the temperature falls below a certain 






1 'W i 



r- 



n 



£> 



li-.""^ 



T. 



«*•: ""i"S 






ii — 



- J 



r 



1 



PUMP RETURN STEAM HEATING SYSTEMS. 



291 




Fig. aoo.— Webster 

Thermoslatic Valve. 

(Old Fonn.) 



prearranged amount less than that of the steam, or to close 
when the temperature rises to that of the steam. The action 
of the valve in this manner causes complete condensation to 
take place in the radiator, so that the vacuum-pump removes 
only the water of condensation and air. It should be noted 
that separate steam supply- and return- 
pipes are required in both the WilUames 
and Webster systems. 

At the present time, Warren Webster 
& Co., sell systems of vacuum and modu- 
lation steam heating. On the following 
page are shown three different radiator 
traps used by them. These radiator traps 
are in principle, miniature steam traps, 
allowing the water and air to leave the 
radiator and closing against the steam. 
Several styles of their traps are shown. 
The application of the various types of 
traps is determined by the conditions, 
varying according to the temperature of the apparatus which 
is to be drained and the quantity of condensation which will be 
thrown down, and whether the return lines are under a vacuum 
or atmospheric pressure. 

Tke Webster Thermostatic or Thermo Valve, Fig. 201, is 
used principally on small units of radiation, is adjustable and 
automatic, permitting water and air to pass, but expanding 
when the plug is surrounded by steam, causing it to seat and 
preventing waste of steam to the return. This valve is intended 
for fairly constant low pressures. 

The valve shown in Fig. 202 is all metallic, automatic, non- 
adjustable and works on the float principle. Air passes out 
around the screw thread spindle. Water surrounding the float 
causes it to rise, opening the port and allowing the water to 
pass to the return pipe. This valve is intended for low pres- 
sure service. Any vapors which may pass to the returns are 
readily condensed in these bare pipes. 

The illustration Fig. 203 shows an automatic thermostatic 



•m 



HEATING AND VESTILATING. 



vulw for the return end of steam radiators, which can be 
UM'cI for widely varying pressures, permitting water and air 
lo pittm while light against steam-leakage. 

136. DUgnuni with Cochrane Steam Stack Heaters. — A 
nunilHT of cross-section cuts of a few representative radi- 
ator trujHt operating on cither the float or the thermostatic 
[irltitiplc are shown in Chapter IX. Lack of space prevents 
llii- dcMcriplion of the various systems manufactured but the 
" KxhauMt Steam Heating Encyclopedia" * contains diagrams 
(if all of the ftdlowing heating systems when used with 
the ('ocliniiie exhaust-outlet valves and feed-water heaters: 




ilpbco Tbermotn. 



Atwak, Hnvinioll. l~ri->*YiH. Or\ot. Doxier. Dunham. Eddy, 
Uainos, llliiwis iXcim-^'rinc Co., Kieley, Kinealy. Ejiebel, 
M.^linc M.MiA.sh, M .Nn-hc.'i.i Mortr-in -Clark. Paul. Piaatiti« 
l^iiVfi-i-nii.il Kfii.il>.V Ki^^.^i■.■B3K-.vk-Bl^-ie^|, Rodiester, 
Si^1t.^;vi^. Sj'wiiiy, >;:ri--Si-.')'.. ThcTm.iirraac- Trane. Van Auken, 

l>.;\v 1%:" :^i-s,' d',r.s.r!.-::> :,- :>if K::ici^y, Mcoiaii, and 
r.'w.iiiw y*\: i--r;--.:',i.. ^^■-:, ■:--.> :.v: ri'pr.vIjCfi ai « reduced 
s.i-v .v.- iSi- ,■.;■.■« .-.i ;A',jL','- 



.-OKE itvd--wxur 



PUMP RETURN SIEAM HEATING SYSTEMS. 293 

system, or live steam is admitted directly through the live 
steam regulating valve. Each radiator is equipped with a 
hand control inlet valve and an impulse check outlet valve. 
The differential controlling valves in the vacuum lines are for 
close regulation. The vacuum pump discharges the water of 



Fig. 104. — Kinealy Vacuum Heating System. 

condensation through a water siphon seal to the feed-water 
heater. This discharge is vented to allow the air to escape. 

Fig. 205. Monash Vacuum Heating System. — Hand control 
inlet valves and Monash noiseless vacuum valves are used 
on the radiators. A vacuum pump equipped with pump gov- 
ernor returns the water of condensation to the heater and the 
air to the atmosphere. 



HEATING AND NTINTILATING. 



Fig. 206. Pasiiize Dijerential Heating System, — ^livc steam 

fe aciritLed thK»ugh a reguLiting valve to either or both halves 
of the s}*stec:. Radiators equipped with thermograde graduat- 
iz:C control \'alves and radiator traD valves, allow the water 



^ • 



!| 






:i. 



^ 



=«: 



TT 






I 



■-.■: ^x- 



mm 







^*r 



< 



"*.. 



* ;=-■ 



^c i^-evi- 



^ . 



. - - i: 



PUMP RETURN STEAM HEATING SYSTEMS. 



295 



of all the radiators so as to cause circulation of steam through 
the radiator, it employs a small jet-pump called an exhauster, 
which can be operated either by water or steam under pres- 
sure, and which is connected to a pipe-fitting in communi- 
cation with a series of exhaust- or air-pipes, each leading to a 




Fig, io6. — Thermograde Poative Differential Heating System. 

thermostatic air-valve attached to each radiator. The ther- 
mostatic air-valve is constructed on the same principle as 
that shown in Fig. 87, and will close at the temperature of 
the steam so that it will discharge air only. A simple dia- 
gram showing the essential elements of the Paul system is 
shown in Fig. 207, opposite, as applied to heating with 



iFF-\rg^> ASL viyni 



Tiffri a. iaidL-pr;s3cre ^"jhc sear ^±e ^<nLZ :i -^kcriarR izito 
t&e ifr. From tae eaia.25t-p^ brxni±i*s :t*:uf oc for sop- 
pLjEiir •kicJl nfffa.D-jr TPiih. stfiazi rzi tiie uscal siiizisfir. Tbc 
Low^r ramaror. cefnir scppSed -¥1^1 a sepanre reciirz- SUnstrates 
the appiLcarii:!! of :ie fasten to x rsri-prpe ;i:6, wfrre tfee 
Gpcer nrSjiZirx iluscnres the ippi2cxt5i:-ii l: 1 oce-pqpe system 
Gt hs^uziL. RiiCin:* frrin: iH ^he rifiiMc? xr^i drips from 




■-. _■:- — L-'iii :-■. >-i.:rT: 



r.ht* -fce-Iines crtizect "s^ltii a tark -.t :'ro;:iv»ir <h«:wn ia the 

"I'l-iCfa-iie f'.r 'i*.z •vi:.er. •■v':':.::: :*:i;. *:c ycrrr^ei out for 
:-r:i:':r \<m. :r •v:ii:j'i 15 rr:j; :c :',>:-:■: irA \> usually con- 

p • • « ._ 

.»•-.._-—, - -n .p. f*,-,.,. ..^.Y'l**!* <■' r< ~ • '■•-.-■. r-- I •■•1 «»•••-», T—. 

,.••- .4iV «>k _ . •• '« ^.— n^ i_. » .^ . .. .^. >». «. .•_. . _ '^S.!^ , , M. I t 

rhe ::.i-:r*ir:. !:«.':v'r/^r. :>c -:•:•:!'■ v- *- / :"-;>>:•.: :Lir^ :-:m which 

z.'-^: r.'jdr the 
- ■ i'r:^ :o the 
^ :~v *'xated 



tiniil— »: -_ -. •-•: ■ - ' - 
... ■ • • • 

I j I I'^l - - ■ ' - ... .f^ . 



^Iri v^* ^ ■ 



I ^•« 



I • 



C'^ 



% I ^» * » 



PUMP RETURN STEAM HEATING SYSTEMS. 297 

on each radiator and on the receiver. These valves open when 
the temperature is less than that of the steam and permit the 
flow of air from the radiator into the exhauster, whence it 
is discharged. Under ordinary conditions the vacuimi pro- 
duced by the exhauster would extend only to the discharge 
orifice of the thermostatic valve; but if the supply of steam 
is restricted and the discharge from the returns sealed, the 
vacuum may extend into the radiators and through the entire 
heating system to the engine. 

In the practical erection of the Paul, system for large build- 
ings the arrangement of pipe is generally similar to that 
shown for the Williames system, except that it is applicable 
to either a one- or two-pipe system of heating and is usually 
such that the exhaust steam first passes through a feed-water 
heater so constructed that the water to be warmed flows 
through a coil of pipes surrounded by the exhaust-steam. 
This is for the purpose of warming the boiler feed-water with- 
out contaminating it with grease and oil. The exhaust-steam, 
after separation of the water of condensation and oil, flows to 
the top of the building, from whence it is conveyed to the 
various radiators and heating-coils as in the system described. 
The system is so arranged that live steam can be used if desired. 

The advantages -of the Paul system depend principally 
upon the quick removal of air from the various radiators and 
pipes, which constitutes the principal obstruction to circulation. 

138. The Johnson System of Hermetic Heating, designed by 
W. S. Johnson of Milwaukee, consists of an air-valve attached 
to a radiator which is constructed in such a manner that when 
the air is once forced out it cannot return. In this case the 
air-valve and also the supply-valve are operated by pneumatic 
pressure controlled by a thermostat located at any convenient 
point in the room, as in the Johnson system of temperature 
regulation. It is intended to be used in connection with the 
Johnson system of heat regulation, and is arranged to produce 
any desired vacuum, by condensation, and consequently any 
desired temperature in the radiator to which it is attached. 

The Van Auken system of circulation is similar to the 



»S HEATING AND VENTILATING. 

Paul sj-stem as already described, in that it has an exhausting 
device attached to a thermostatic air-valve in essentially the 
sjJT.e manner. The thermostatic movement, however, is 
regulated by change of temperature in the room and operates 
both adnr.ission- and air-valve for each radiator, as in the 
Tohnscn svstem. The air-valve is so constructed that it 
av~i:s air to the radiator when the temperature of the room 
is :v.v hich and discharges it ihrouirh the exhauster when the 
temperarure is to^^^ low, thus controUini: the temperature by 

:59. Cooibined Hi^i- and Low- pr e ssur e Heating-systems. — 
In =cj.r-v jlI: s^s:er.:s c: hearing ^-[ih =xhaus: steam it is 
ne-Jrss^n ::• arr.:.^^:^ :r.f p:vin^ Sv' iha: a: limes live steam may 

Z^.i-LT -LUC rrj.". "LX'SSir."' rt: ->c'^ >r: - 



• ^ - «»« 



"^"—l--.. 1:? J-l"\.. II. "JC-.- ...'. 



» - , 



i-< 



^ -■'. - 



?T»rzcrs. 



r:"<surt 


>!ijrr. 


• 


rarried in the 






1 • 


::rs. while the 


> r^ -« *i <« L *^ 


■A •"•"-* 


• 


rrrssure steam 


« « ■ - 


r JLT".".! 


^ ^^ 


■*u:tv: in pres- 


n"'-'. ~. «' -I' " * 




Ir. 


i""^:- cise the 


:\.><v> : 


• 


r 2L , 


r chamber at 


«« ft * *% ^ 


1 ^ • ' 


** • 


ihc S:IIer by 


k > • • -^ • ■ ft 




— : ., 


:'7»il cflements 


ft 


> -■.>!, 


• 


:: :2c .V^oany 


.-.,,^ 


- ^v > 


^ 2* 


:ru::;n :: the 


>!.."' 


* « 




--:-:r::a::calIy 


y~ ',\ ' 


^.*v, .". 


■ : 




^ 


^ 


"^ _ ^ ■' 


• > . : zeatinjr 


"- 


* 




^" :; rvtum 


•\ 


X _ 


- 


■--::>. The 


■^ 






.■pcra:e 




^ 




*^>-~:> :j 



x.:r:v 



PUMr RETURN STEAM HEATING SYSTEMS. 



299 



operating the piunp. The tank is connected to the suction 
and located above the pump. When the tank is full of water, 
the steam-pump ie put in operation by the rising of the float, 




which opens the steam-vatve. When the tank is empty, the 
float falls, closing the steam-valve and thus stopping the pump. 
A pump-governor consisting of a float-trap with outside 
connections to a steam-valve, as described by F. Barron,* 
s shown in Fig. 209. 

* Beating and Vcniitalion, March, 1854. 



sw* 



HEATTSG AKl' TETTrLATISG. 



serdun. Tip. rar, 1e liuF cast the fl.- ipi i of liie ji pftf^ iamt, 
the -t-ah% jor siq^ihing steam 

gTT^pif' pan. and is ccnDectBd 
in- EI imemal 'ieva to lie 

"•iec tilt task is sXied lie 
TLh^ -wit fat tpened and the 
pmnr 'will ^oeriie. and iriiai 
tJK tent » ennirr tic vaJpe 
viL *K ciniffi:. and lit psnqi 
wit 5i.;p 

tr.-nr rh; tumir. tin £iiadied 








PUMP RETURN STEAM HEATING SYSTEMS. 



301 



The figure shows the loop returning the water from a 
separator, attached to an engine-main, to a boiler above the 
separator level. " From the separator drain leads the pipe 
called the * riser,' which at a suitable height empties into the 
horizontal. This runs back to the drop-leg, connecting to the 
boiler anywhere under the water-line. The riser, horizontal, 
and drop-leg, form the loop, and usually consist of pipes vary- 
ing in size from three-quarters of an inch to two inches, and are 
wholly free from valves, the loop being simply an open pipe, 
giving free communication from separator to boiler. (Stop- 
and check-valves are inserted for convenience, but take no 
part in the loop's action.)'' Supposing, for example, the boiler- 




Fig. 211. — ^The Steam Loop. 



pressure to be loo pounds and the pressure at the separator 
reduced to 95. " The pressure of 95 pounds at the separator 
extends (with even further reduction) back through the loop, 
but in the drop-leg meets a column of water (indicated by the 
broken line) which has risen from the boiler, where the pressure 
is 100 pounds, to a height of about 11 feet, that is, to the hydro- 
static head equivalent to the 5 pounds difference in pressure. 
Thus the system is placed in equilibrium. Now the steam in 
the horizontal condenses, lowering slightly the pressure to 94 
pounds, and the colunm in the drop-leg rises 2.3 feet to balance 
it; but meanwhile the riser contains a column of mixed vapor, 
spray, and water, which also tends to rise to supply the hori- 
zontal, as its steam condenses, and being lighter than the 



302 HEATINa AND VENTILATING. 

solid water of the drop-leg it rises much faster. By this 
process the riser will empty its contents into the horizontal, 
whence there is a free run to the drop-leg and thence to the 
boiler." 

142. Reducing-TalTes. — The reducing-valve is a throttling- 
valve arranged to be operated automatically so as to reduce 
the pressure and also to maintain a constant pressure on the 
steam-mains. A great many fonns of these valves are in 




Fig. 211. — Hole's Reducing- valve 



common use. In one a diaphragm of metal or rubber is em- 
ployed, as in Fig. 212, The low-pressure steam acts on one 
side of the diaphragm, a weight or spring which may be set at 
any desired pressure on the other side. This diaphragm is 
connected with a balanced valve which is moved to or from 
its seat as less or more steam is required to preserve constant 
pressure. Since the pressure in the main steam-pipe does not 
effect the motion of the valve, its position will depend upon 
the pressure on the two sides of the diaphragm. The pressure 
on one side is that due to the steam which has passed through 



PUMP RETURN BTEAM HEATING SYSTEMS. 303 

the valve, and that on the other to a weight or spring which 
can be set at any desired point. 

Another form of redudng-valve with differential piston and 
diaphragm is shown in Fig. 213, and is described as follows: 

Steam from the boiler enters at side " steam inlet " and, 
passing through the au.xiliary valve A', which is held open by 
the tension of the spring S, passes 
down the port marked " from 
auxiliary to cylinder," under- 
neath the differential piston D. 
By raising this piston D the 
\'alve C is opened against the 
initial pressure, since the area 
of C is only one-half of that of 
D. Steam is thus admitted to 
the low-pressure side, and also 
passesuptheportA'.V underneath 
the phosphor-bronze diaphragm 
00. When the low pressure in 
the system has risen to the re- 
quired point, which is determined 
by the tension of the spring S, 
the diaphragm is forced upward 
by the steam in the chamber, the 
valve K closes, no more steam 
is admitted under the piston D. 
The valve C is forced onto 
its seat by the initial pressure, 
thus shutting off steam from 

the low-pressure side. This action is repeated as often as the 
low pressure drops below the required amount. The piston 
D is fitted with a dash-pot E, which prevents chattering or 
pounding. In another style of construction a piston acted on by 
the low-pressure steam serves to open or close a balanced valve 
^n amount sufficient to maintain the steam-pressure constant. 

143. Transmission of Steam Long Distances. — It is fre- 
<3uently necessary to transmit steam long distances under- 




FlG. 313.— Majon's Reduciag-valve. 



304 HEATING AND VENTILATING. 

ground, and in many cases this method gives better financial 
returns than the construction and operation of a large num- 
ber of small and isolated plants. A number of plants, in which 
steam has been conveyed long distances in pipes laid under- 
ground, have been constructed for the purpose of heating 
portions of cities, and also various buildings belonging to the 
same public institution. 

In the heating of various buildings which belong to the same 
public institution this system of heating has proved a great 
improvement in many respects over that of separate heating- 
plants, although it is doubtful if in a single case it has ever 
resulted in the lessening of expense for fuel. 

The three important requisites in the construction of such 
plants are, first, a removal of all surface-water so that it cannot 
possibly come in contact with the steam-pipe; second, provision 
for taking up expansion of pipe and keeping it in proper 
alignment; and, third, insulation of the pipe from heat losses. 

The first condition, which is the most important of all, is 
also the most likely to be overlooked, and many failures to 
secure economic transmission have been caused by allowing 
the surface-water to come in contact with the heated pipes. 
This water can be removed by the construction of a drain 
beneath or by the side of the pipe-system, provided with proper 
outlets. A perfect drainage-system for the soil is in every 
case an essential requisite for success. 

Provision for expansion may be made by the use of expansion- 
joints, or by the use of elbows and right-angled offsets arranged 
to partly turn as the line expands. The writer has had experi- 
ence with various forms of these joints, and found nothing equal 
to the straight expansion-joint, Fig. io8, which should, however, 
be constructed so that it cannot by any possible accident be 
pulled apart; this may be done either by use of an internal 
lug or external brace. These joints should be thoroughly 
anchored, so that they will stay in position, and should be placed 
sufficiently close together to take up all expansion without 
strain on the pipe-line. If the ordinary slip-joints are used, 
they will need to be placed at distances of about 120 feet apart. 



PUMP RETURN STEAM HEATING SYSTEMS. 305 

The pipe between the joints should rest on rollers or connect- 
ing hangers which permit its free motion. If elbows and off- 
sets are employed to take up expansion, there will be an 
abrupt change in grade, and if any part dips below the main 
steam-line it should be drained by a pipe connecting to a trap 
or to the return. If bends convex upward are necessary, means 
must be provided for removing the air. 

In general, in systems where the steam is transmitted long 
distances the best results will be possible only when the boiler- 
plant can be located on lower ground than the buildings to 
be heated, so that the water of condensation may be returned 
by gravity. This cannot always be done, and in many cases 
it will only be possible to return the water of condensation by 
a pump located in one of the buildings to be heated, and 
regulated by a pump-governor. This in some cases may 
involve more expense than will be warranted by the saving due 
to returning the water of condensation. 

144. Pipe Sizes for Vacuum Steam Heating Systems. — 
Since the amount of radiating surface is usually based on 
the heat required for zero weather out of doors, radiators for 
either vacuum or atmospheric steam heating system should be 
at least as large as required for gravity steam heating. 

The main supply pipes for vacuum pipes are the same as 
those for the equivalent gravity steam heating installations. 
The branch supply pipes are practically one-half the diameter 
of those for the ordinary two-pipe steam system. The branch 
and the main return pipes are about f the diameter of the return 
pipes of the two-pipe steam system. 

All the supply pipes for the modulation atmospheric steam 
heating systems should be sized liberally to prevent sensible 
loss of pressure except at the hand or automatic regulating 
valves at the radiator inlets. 



CHAPTER Xn. 
HOT WATER HEATING SYSTEMS. 

145. In the gravity circtUating system, the water is caused 
to flow by the diflference m density of the heated water from 
the boiler and the return water from the radiators. In the 
forced circulating systems, the circulation is assisted by pimips, 
steam jets or air lifts, etc., which are sometimes only used in 
severe weather or used in a part of the heating system where 
diflScult conditions are to be overcome. 

In Chapter X, the general question of the amoimt of heat 
and radiating surface required for hot-water heating is taken 
up as being inseparable from that for steam heating. 

146. Methods of Piping Used in Hot-water Heating. — 
A system of hot-water heating should present a perfect system 
of circulation from the heater to the radiating surface and thence 
back to the heater through the returns, an expansion-tank 
being provided, as explained, to prevent excessive pressure 
due to the heating and the consequent expansion of the water. 
The direct-circuit system, as described for steam-heating, 
Fig. 189, is well adapted for hot-water heating, and has been 
used to a limited extent. When this system is employed for 
hot-water heating two connections are usually taken off from 
the return riser at different levels for each radiator, as shown 
in Fig. 223, although in some cases a single connection is made 
and a radiator of ordinary form employed, otherwise the method 
of piping is exactly similar to that described for steam-heating. 

The system of piping ordinarily employed for hot-water 
heating is illustrated in Fig. 214. In this system the mains 
and distributing pipe have an inclination upward from the 
heater; the returns are parallel to the main and have an inclina* 

306 



HOT-WATER HEATING SYSTEMS. 



307 



tion downward toward the heater, connecting at its lowest 
part. The flow-pipes are taken from the top of the main and 
supply one or more radiators. The return-risers are connected 



i 

n 

•g 

a 
I 



1 

(Z4 



I 

-a 




» 



'a 

(A 

c5? 



I 



CI 



with the return-pipe in a similar manner. In this system great 
care must be taken to produce nearly equal resistance to flow 
in all the branches leading to the different radiators. It will 
be foimd that invariably the principal current of heated water 
ivill take the path of least resistance, and that a small obstruc- 



30S HEATIXG ASD VEXTILATING. 

tion, any irregularity in piping, etc is sufficient to make vay 
great differences in the amount of beat received in different 
parts of the same 5\3tem. For instance, two branch p^>es 
connected at opposite ends of a tee. which itself is connected 
by a centre opening to a riser, are almost certain to have an 
irregular and uncertain circulation. 

The method of piping generally adopted for the closed or 
high-pressure sjstem is that of the complete-circuit or one-pipe 
system, as illustrated in Fig. 1S9. This system when now 
employed is used only for moderately low pressures, and a 
safety-valve is pro\'ided on the expansion-tank to prevent 
excessive pressure. In this system, or, in fact, in any of the 
systems for hot-water heating, the level of the return-pipe can 
be carried below that of the heater without bad results. The 
method of applying this system is shown in Fig. 215, which is 
similar in many req>ects to that used in the Baker system of 
car-heating. 

The expansion-tank must in everj* case be connected to a 
line of piping which cannot by any possible means be shut 
off from the boiler. It does not seem to be a matter of impor- 
tance whether it is connected with the main flow or with the 
return. 

Single-pipe systems for hot-water heating have been used 
to some extent. In this case there is a gradual flow of the heated 
water to the top, and the consequent settlement of the colder 
water to the bottom. The form of piping would be essentially 
the same as that sho\Mi in Fig. 1S9 or 190. Separate flow 
and return risers are used. The flow risers are connected to 
the top of the mains and the return risers to the bottom of the 
mains. Where the supply and return water have to flow in 
opix^^ile directions in the same pipe, the horizontal length of 
the main cannot exceed about 12 feet. Usually, return mains 
are connected to the end of the flow mains so that the water 
currents are not opposed. 

The writer erected such a system at one time as an experiment 
and found that it worked well after the waicr had .»nce become 
heated. Where there is no ubjeclii)n l.» a >y>icm which heats 



HOT-WATEB HEATING SYSTEMS. 309 

slowly, this would probably do well on a small scale, but could 
not be recommended for an extensive job. 

147. Expansion-tank. — ^An expansion-tank will be needed 
in hot-water heating systems. With increase of temperature 



1 










rr^- 












5 


'■■•fl 











from 40" F. to the boiling-point, water expands 4.33 parts 
in 100, or over 4 per cent. The force of expansion is nearly 
irresistible, and the increase in volume due to it must be pro- 
vided for, so as not to produce a dangerous pressure. 




le f o rti e th <rf the tatal abial < 
Icsti «f beater, fi^ws, aad rj i fa l uih It ■ 

to the beatBig ^f^H^ b tmdt 

m vobaoK, and sfatnU be pbccd oa > lenl sooeHbat above 

that ot the h^gbot ragtag lorfacfc 

Tf lliiii ii fii Tw lai iiiiiBili iaii iii ai fi iiiwi ill In i niiii 

Am Ibe taak b cmiKCtcd wkb tbe outside air I7 a vcat-fiipF. 
and IB tliis fa«» tbe pt tssui e "*™l^ 
win be atmospheric; tbe piusuie oo 
tbc beating system win depend oo the 
diirtancf from tbe water-levd in the 
tank, eacb foot com^nndtog'to 0^15 
poaod per ^qmic inch (z-ti Eeet betng 
equh-alect to one pound of pcessoie at 
212'- F.;. 

148. Closed ^stens.— In case a 
pressure in exce^ ot tbe atmosphere 
b required, tbe Ment pipe is dosed 
and a 5afet>--*'al\'e attachied which will 
open wben the pressure reaches the 
desired ptant. By increasing the pres- 
sure on the s\-stQn the boiHng tem- 
perature of the water wiB be much 
increased, and hence it will be possible 
to maintain a higher temperature 

throughout the system. M showing the increase m 1 

ature of the boiling-point with eicess of pressure, the fd 

table is inserted. 

Pressure systems of hot-water heating were used '■ 

time to a considerable ertcnt in England, under wb 

known as the Perkins * system, in which small pipes aod e 

ingly high pressures and temperatures were used. 

also been used to some extent in this country In the ] 

system of car-heating. 

• Hood'* "HeMing Mtd VcntflMiog ot Biiadiae<L." 




HOT-WATER HEATING SYSTEMS. 



311 



The advantages of the pressure system are those which are 
due simply to the use of higher temperatures and smaller radi- 
ating surfaces; the disadvantages are the danger of an explosion 
which would be likely to happen were the safety-valve inoper- 
ative, or did any part of the apparatus give way. The sudden 
liberation of a considerable body of water having a temperature 
above the boiling-point would result in the instantaneous pro- 
duction of a large amount of steam, which might produce dis- 
astrous results. 



Pressure. 


Temperature of 
Boiling-point 










Pounds 

per Sq. In. 

above 


Equivalent Head, 
in Feet. 


(degrees P.). 


Atmosphere. 






o 





212 


5 


12 


228 


lO 


24 


240 


IS 


37 


250 


20 


49 


259 


25 


61 


267 


30 


74 


274 


35 


87 


280 


40 


100 


287 


45 


"3 


292 


50 


125 


297 


55 


137 


302 


60 


151 


307 


70 


177 


316 


80 


205 


324 


90 


230 


332 


100 


257 


338 


125 


324 


352 


150 


393 


365 


175 


463 


378 


200 


534 


388 









With the open expansion-tank it seems hardly possible that 
any serious accidents could result even from the most careless 
management, since the escape of steam from the top of the 
expansion-tank would prevent the accumulation of pressure. 
To prevent accident the expansion-tank should be connected 
to the heater by a pipe protected from frost and without stop 



SI2 



HEATING AND \'ESTILATIXG. 
) render i 



or valve, so as to render it impossible to increase the pressure 
on the system by stoppage of the comiection. 

It is desirable to provide the expansion-tank with a glass 
water-gauge lowing the depth of water, and a anmection to 
the supply-pipe for adding water to the system. In case tfae 
e\pansion-tank occupies a cold location where it might freeze 

Jin extreme weather, a small pipe ooa- 
nected with the circulating s>'5tem, in 
addition to those described, should 
be run to the tank and connected 
at a higher le\-el than the expansion- 
pipe, so as to insure circulation of 
warm water. 
149. The Honeywell Pressure Sys- 
tem. — By the use of a mercury- safety 
valve called a '' Heat Generator," 
located in the pipe connecting the 
expansion-tank with the rest of the 
hot-water heating system, they are 
enabled to use a hot-water pressure 
system, without any sacrifice of safety. 
The '■ Heat Generator " is essentially 
a safety-valve preventing any flow of 
water to the e.Tpansion-tank until a 
pressure of about ten pounds above 
^^^ atmospheric is reached, when any 

^^M Fic. 117. — lltiu^traiing posi- excess of pressure is relieved by 
^m Uonof Mciturjand WaiCT fordng water through the mercury 

^^M when Generator is Produdoe , ■ , ,. .1 ■_- 1 • 

^H no Pinsurc ^*' "^^'^ ^'^ expansion -tank, which is 

^V open to the atmosphere, .^s the ' 

mercury seal is pro\ided with a large mercury- chamber at 

the bottom of the escape tube, a drop in pressure of only 

one-half pound is sufficient to draw in water from the expansion- 

■ tank, thus pre\-enting the formation of a ^-acuum in the system, 
which would cause the intiltration of air into the heating sys- 
tem. The dexnce is so made as to prevent the mercury being 
either forced out into the expansion pipe or sucked back into 



HOT-WATER HEATING SYSTEMS. 313 

the heating system. The accompanying cut shows the ** Gen- 
erator '' in cross-section. 

150. Accelerated Hot-water Systems are those in which 
the water in the risers is superheated, causing the liberation 
of steam bubbles as the water ascends and the head or pressure 
on the water is lessened. If injectors, pulsometers, or air 
lifts etc., are used, they fall under the head of pumped hot-water 
systems, only using another kind of pump. 

Forced or pumped hot-water systems in which the circula- 
tion of the water is accelerated by pumping allow the use of 
smaller pipes. In an installation of this character the relative 
cost of the piping and the cost and upkeep of the pump are the 
commercial determining features. This system is especially 
adapted to installations where exhaust steam at less than atmos- 
pheric pressure is available for heating purposes. The heat- 
ing water is circulated through the tubes of a surface condenser 
or a closed heater and a partial vacuimi maintained except 
in severe weather. 

Centrifugal or rotary pumps are usually employed. The 
centrifugal pimips will not build up an excessive pressure in 
case the mains should be shut off, and will have a fair efficiency 
under these conditions. 

Compute the pipe sizes from either the amount of radiating 
surface or the heat required, by computing the volume of water 
for each main for the assimied temperature drop (30 degrees). 
Then assume some velocity of flow and check the total friction 
heads for each path of the water all of which should be nearly 
equal. Allow for the difference in densities in the risers. 

All mains should have gate valves for close adjustment of 
the relative flow. 

151. Hot-water Circulation Systems. — There are several 
systems in use in which hot water after being heated by exhaust- 
steam is circulated by pumps or otherwise through the various 
radiators and heating-coils. Of these systems that of Evans 
& Almirall is in most extensive use, of which one form is shown 
in the diagram. Fig. 218. As illustrated, the exhaust-steam 
from the engines CC and pump B passes through the heater 



HEATING AND VENTILATING. 



shown at A, where it is in part condensed and the remainder 
discharged through the open exhaust-pipe B. The exhaust- 




steam in this heater surrounds brass or copper coils through 
which the water flows, thereby taking up heat from the steam. 



HOT-WATER HEATING SYSTEMS. 315 

The water after being warmed in the heater A is circulated by 
the pump B (which is represented here as a piston-pump, but 
is usually of the centrifugal or rotary type) through the vari- 
ous pipes and radiators RR constituting the heating system. 
The pump simply performs the work of circulating the water 
at the required velocity and overcoming the friction, as the 
pressure on both suction and delivery sides is otherwise the 
same. By means of the pump any desired velocity can be 
attained with a corresponding regulation of the temperature. 

An auxiliary live-steam heater is shown at Z), which is 
provided with a coil through which the live steam can pass, 
and is arranged so that the water can be circulated through it 
as needed to supplement the exhaust-steam heater. In some 
instances an economizer or heater in the smoke-flue is employed 
alone or in connection with the other heaters. This system 
is particularly well adapted for the warming of buildings with- 
out causing excessive back-pressure on the engines, although 
they may be situated some distance from the supply of exhaust 
steam; it has been extensively employed for utilizing the 
exhaust steam of electric-light plants for warming buildings in 
connection with large institutions and in cities and villages. 

The Yaryan system is essentially the same as the Evans & 
Almirall system. It seems to differ only in minor details of 
construction. 

The Osborne system differs in that the exhaust steam is 
circulated to a heater located in the building to be warmed; 
no pump for circulating water is used; the transfer of heat 
from the exhaust steam causes a circulation of water through 
the heater and the heating system in much the same manner 
as in the ordinary systems of hot-water heating. 

152. Pipe ConnectionSi Hot-water Heating Systems. — ^The 
general arrangement of hot-water radiator piping is to have 
"tte supply and return pipes on opposite ends of the radiators. 
'Jhe supply may be either top or bottom, but the return is at 

bottom. Both pipes may be at the same end, and provided 
radiator is tapped large enough, both connections can be 
tnade at the same place by using a special valve or fitting. 



316 HEATING AND VENTILATING. 

If the system of circulation adopted is the complete-circuit 
system, as in Fig. 189, in which the heating main is first taken 
directly to the top of the building and thence nm horizontally 
to the various lines of return risers, the system of construction 
would be essentially the same as that described for a steam- 




heating plant. The main riser should connect into a drum, 
from the top of which the distributing pipes leading to the 
return risers are taken. The size of the distributing pipes 
should be proportional to the amount of radiating surface, 
and the various distributing pipes should be arranged so that 
the resistance in each will be substantially equal. The flow 
connection for each radiator should be taken off at a point 



HOT-WATER HEATING SYSTEMS. 317 

about level with the top of the radiator, as in Fig. 223, and 
the return should enter the same pipe at a point below the 
radiator. A valve affording as little resistance as possible 
is to be put in each connection. Hot-water heating systems 
have been erected in which the radiators are joined to the 
riser by one connection only; and while this system seems 
to be somewhat slower in heating than that with two connec- 
tions, it is otherwise quite satisfactory. 

In the system commonly employed the main and distribut- 
ing pipes are erected in the basement, as shown in Fig. 214. 
An offset from the main to the foot of the riser has usually to 
be made, which should be done as from the steam main in Fig. 
193, and in such a manner as to take the flow from the upper 




MfTinM 






3 



PUMRT 



[0^ 

^""^ Ne.3 

Fig. 220. — Connections to Mains, Hot-water Heating. 

part of the pipe; such a connection is also shown in No. 3, 
Fig. 220. The connection to the main return may be made on 
the side or at the top, as convenient. In some instances a tee 
turned at an angle and a 45-degree elbow can be used with 
good results, as shown at No. 2, Fig. 220. The method of 
connecting shown at No. i should only be employed in case 
the room is not sufficiently high for connections, as shown at 
No. 3, as its use is attended with doubtful success in many 
cases. 

In taking off branches from the top of a riser a tee should 
seldom or never be employed, since it will be found that if 
for any reason the current becomes established in one direction 
it will be very difficult to induce it to flow in the other. When 
branches running in opposite directions have to be taken 
from the main riser, long-radius tees, as shown in Fig. 63, 
should be employed; but unless the riser is long it will in gen- 



818 



HEATING AND VENTILATING. 



eral be better to erect a separate line for each branch. Pre- 
cautions should be taken in every case that the junction of 
two currents shall not exert an opposing force which will impede 
the circulation. 

The connections to radiators for this system need to be 
made in such a way that the horizontal branches which are 
taken oflf from the risers will receive a strong current of water. 
There is a tendency for water to flow directly in the line of 
motion, and to the highest radiators in the system. This 
renders it necessary to increase the resistance in the riser 
beyond the branch a greater or less amount in order to induce 
circulation into the side connections. This may be done in 




3^ 



Fig. 221. — Connection to Radiators, Hot-water Heating. 

several ways, as shown below: (i) by connecting the radiator 
to an elbow placed on the main pipe and continuing the main 
pipe from the side opening of a tee or Y, as shown at A and B; 
or (2) by using a reducing fitting, as shown at C, and continuing 
the riser with a reduced diameter. The return connections 
can be made in a similar manner, but they will in every case 
work well if the return riser be run in a direct line and the 
connection be made into the side opening of a Y. 

153. Position of Valves in Pipes. — If a valve has to be used 
on a horizontal pipe it should be located so as to afford the 
least possible obstruction to the flow of water in the required 
direction. If a globe valve be used with the stem set vertically, 
Fig. 222, it will form an obstruction sufficient to fill the pipe 
nearlv full of water; if the stem be placed in a horizontal 



HOT-WATER HEATING SYSTEMS. 319 

direction the flow of water will be less impeded. Globe valves 
iorm a great obstruction to the flow in water-heating pipes, and 
under no circumstances should they be used for that work. In 
the case of steam-heaUng they are less objectionable, provided 




-Illustration of Water Held by Globe Valve. 



they are located in such a manner as to permit free drainage 
of the pipes. In general, angle or gate valves can be used, 
however, in every place with better satisfaction. 

For hot-water heating special valves have been designed, 
which when open offer no special impediment to the flow, and 
which close sufficiently tight to prevent 
circulation, although not sufficient to pre- » > 
vent leaks. I- 

154. Size of Pipes for Hot-water Radi- 
ators.— Method of computation of the 
velocity with which circulation will take 
place in a hot-water heating system with- 
out friction has been considered in Chapter 
IV. In some instances this velocity is 
increased by bubbles or particles of steam 
which pass up the main risers and reduce 
the specific gravity of the water m the ^j^^ ^op and Bottom 
ascending pipes to such an extent that the Connections, 
actual velocity produced is much in excess 
of what would have been possible had no steam formed. This 
condition is usually undesirable, as it is often accompanied with 
more or less noise, but several rapid-circulating systems have 




Tecenthr been oeacned to ^licnr liie ^cDsrsSicm cS a sazall 
ijTiiiTixirr cc $;TfiaTr.. Ii ^olM sc<i tit renonuneDdfid Aal htBUss 
be niL 1:1 fmrib TnaTmffr £5 tc> prcdiHX' fn.fa.Tr in snr pait unless 
ic inffdcnftd 

Tbt bfiia idnii i^ rfven c»f frani rafiLnmr smaryf off xmoos 
kzaaf- hhsr iJ:%adT been rcmaoerec kuc. £5 tarir thfrma,! mut 
ch'SL nf rj nit s^zraux- is iicjjutnz t'j liit c:i:mzi£r cf ant poand 
a: Viler :int decret jl isnn^ertnrt.. ri i chft t:- caxrgnrlt irom 

lit dtit ifvct ; lilt voiii cc vuer reoinred. £zid r the 

w. ^ _ 

mimie: cc citaz ififii needed t: beti saa: sgnETt ioDl <rf 
mdiiLzmr siziar^t. 

Til 5:iiinvin£ tLTiif £5^'c^ li* duit iKsr^essLrr iar ranjpirniig 
lii --iiiumi :c vLier r^jubsi t; si^ttti^ riidu^nzir sxrrtact for 






_ -nmcaiiiP^ lunaio: ar r r r r r 

r amefiu.* ixn ▼ruur n Tuduinr ,ac jrc j?c jar rar 

seiiiut; ii»n". ikt nmr . .,= ~5 it :f 

"V-ffinn'- 11 .'L n voiis: ]kaun& :r.. _..- tc iJ" tc 53 ic r* 5L t-t 

luNm !=■ .^7 sr ri-i aS*" 

~:* ij' . u jr»= jaf r-o 

■"i» • '•' - «." » ^"^ ^ T J3 r t ^ 

3uLd-ii-r ■• ' r-: : — -: 

— r-^ 

l»-idi.Li'r .1*1-; — ~r 



« 


« 






-.■^f 


r ;- r a^}- 




^ - 


r ,-:rf; r r.ac 


- 


. 


r .1-:^ r 3r: 



ii.iir :•■ 1:.: ': •' ~ v.! v:.!.-: .:u v. -- •: ;> :>;r ji.ur vt 

_ * I* .... •- •■ » .. . . I . . ... • •• a «« ^-^llii 



HOT-WATER HEATING SYSTEMS. 321 

Let w equal the weight of water per cubic foot, let H equal total heat 
per square foot per hour from radiator, R total radiating surface, Q num- 
ber of cubic feet of water per hour, A area of pipe in square feet, a area 
of pipe in square inches, v velocity in feet per second as given in table, 
page 127, V equal velocity in feet per hour, T loss of temperature of water 
in radiator. We have the following formulae: 

(i) fl=i44/l. 

(2) F= 36001; 

Total heat divided by heat given off by i 
cu.ft. equals total number of cubic feet. 



y V HR ^ 

(3) — =0^ 
wT 



(4) ^=-^=^=— . From which 
V 36001; 144 

(5) 0= 25<^»- Equate (3) and (5), and 
2$avwT 



(6) R= 



(7) a= 



H 
HR 



2$wvT 



By taking special values corresponding to temperatures of water and 
of surrounding air we can reduce these formulae to simple forms. Thus, 
if the temperature of the radiator is 180® and of the room 70®, the total 
heat-units given off per hour, Hy will be 165. If we further assume that 
the water in the radiator cools during the circulation a certain amount, 
say 10 degrees, T will equal 10, weight of water w will equal 60.5 pounds 
and we shall have formulae 8 and 9: 

(8) R=^g2av 

(9) a= — 

92V 

For the above condition the radiating surface is equal to 
92 times the area of the main pipe in square inches times the 
velocity of the water in feet per second; and further, the area 
in square inches is equal to the radiating surface divided by 
92 times the velocity. The velocity in feet per second will 
depend upon the height, the difference of temperature, and 
amount of friction. 



322 



HEATING AND VENTILATING. 



The following table gives relations of radiating surfaces to 
areas of main pipes, friction neglected. For distances less 
than 200 ft. suflGicient allowance for friction will be made by 
making the main one size larger than required by table: 

AREA AND DIAMETER OF HOT-WATER HEATING-MAIN, DIRECT 

RADIATION.* 

Difference of Temperatuiu:, 10 Degrees. 



(I) 


(2) 


(3) 


(4) 


(s) 


Height. 
Feet. 


Velocity Water 
Feet per Second. 


Multiply each 

100 S<^uare Feet 

Radiating Surface 

for Area Main by 


Multiply Square 
Root Radiating 
Surface for 
Diameter by 


Equivalent Head 
in Feet. 


I 


0.335 


3.26 


0.205 


0.0015 


5 


0.750 


1-45 


0.133 


0.0081 


10 


1.06 


I 03 


0.113 


0.017 


15 


1.28 


0.85 


0. 104 


0.025 


20 


1-5 


0.723 


0.095 


0.035 


25 


1.67 


0.65 


0.091 


0.044 


30 


1.83 


0.59s 


0.087 


0.052 


40 


2,12 


513 


0.081 


0.072 


50 


2.37 


0.46 


0.076 


0.088 


60 


2.59 


0.42 


0.072 


0.105 


80 


3.00 


0.362 


0.068 


0.142 


100 


3-35 


0.324 


0.064 


0.176 



* As illustrating the use of the table, compute the area of main pif>e needed 
to supply 350 square feet of direct radiation situated 25 feet above the heater. 
The area is obtained by multiplying 3.5 by 0.65, which will equal 2.28 square 
inches. The diameter can be found from this, or it may be obtained from 
column (4), by multiplying the square root of 350 by o.oqi. The square root of 
350 is 18.7, the product is 1.7. The pipe used, if the distance is about 200 feet, 
should be 24 inches in diameter. 



In the above table column (i) gives the height in feet; 
column (2) the velocity corresponding to the head for a reduc- 
tion in temperature of 10° F.; column (3) is the area in square 
inches, neglecting friction, for each 100 square feet of radiating 
surface; column (4) is the corresponding diameter of pipe 
required for each square foot of surface, and is to be multiplied 
by the number of square feet of radiating surface to give the 
diameter for any given case; the actual diameter should be one 



HOT-WATER HEATING SYSTEMS. 323 

pipe size greater; column (5) is the equivalent head which 
would produce the same velocity if falling freely in the air. 

The preceding table is in the same form as that given for 
diameters of steam-main. If we consider 10 feet as the aver- 
age height or head producing circulation for the first floor, it 
will be seen that we shall need, neglecting friction, one square 
inch in area in our main pipe for each 100 square feet of radia- 
tion, or the diameter of our pipe would be found for this case 
as equal approximately to I of the square root of the radiating 
surface in square feet. 

If the temperature of the water be supposed to change 20° in 
passing through the radiators, the required area of the main 
would be one-half of that given by the table; if 15°, two-thirds, 
etc. 

In hot-water heating the return-pipe must have the same 
diameter as the supply-pipe, since there is no sensible change 
in bulk between the hot and cold water. 

We may take as a practical rule, applicable when less than 
200 feet in length: The diameter of main supply- or return-pipe 
in a system of direct hot-water heating should be one pipe-size 
greater than the square root of the number of square feet of radiat- 
ing surface divided by 9 for tlie first story, by 10 for the second 
story, and by 11 for the third story of a building; for indirect 
hot-water heating multiply above results by 1.5. 

The table given for commercial sizes of steam-mains in a 
single-pipe system of heating applies with accuracy to systems 
of hot-water heating and is easily and quickly applied. The 
table is to be used as explained for steam-heating. 

155. Combination Systems of Heating. — Several methods 
have been devised for using the same system of piping alter- 
nately for steam or hot water as the demand for higher or 
lower temperature might change. The object of this is to 
secure the advantages which pertain to the hot-water system 
of heating for moderate temperature and to steam-heating 
for extremely cold weather. As less radiating surface is 
x^equired for steam-heating, there is the advantage due to reduc- 
tion in first cost. 



324 HEATING AND VENTILATING. 

The combination system of hot-water and steam heating 
must require, first, a heater or boiler which will answer for 
either purpose; second, the construction of a system of piping 
which will permit the circulation of either steam or hot water; 
third, the use of radiators which are adapted to both kinds of 
heating. 

These requirements will be met in the best manner by 
using a steam-boiler provided with all the fittings required for 
siteam-heating, but the addition of an expansion-tank is required, 
which must be arranged so that it can be closed off when the 
system is required for steam-heating. 

Of the diff'erent systems of piping, that designated as the 
complete-circuit or one-pipe system (Fig. 189) is the only one 
which is equally well adapted for both hot water and steam. In 
case that system cannot be conveniently installed, the one 
shown in Fig. 214 for hot water will be found to give fairly 
good results, it being objectionable in steam-heating only 
because of the fact that the condensation in the main pipe 
flows against the current. The radiators and connecting pipes 
should be of the form required for hot-water heating, but the 
proportions and dimensions the same as for steam-heating. 

While this system has many advantages in the way of cost 
over the complete hot-water system, yet the labor of changing 
from steam to hot water will in some cases be troublesome, 
and should the connections to the expansion-tank not be 
opened, serious results would certainly follow. 

A combination hot-air furnace and hot-water system has 
been employed to considerable extent. In such a case the 
water-heating surface is obtained by inserting a coil of pipe or 
suitable vessel into the hot-air furnace, and certain rooms and 
portions of the house are warmed by the heated air directly 
from the furnace, while other parts are heated by the circula- 
tion of hot water. 

This system is an admirable one from every point of con- 
sideration, theoretically; but practically it is a very difficult 
one to design and construct in such a manner that the supply 
of heat to the different rooms shall be positive and well dis- 



HOT-WATER HEATING SYSTEMS. 



325 



tributed. Fig. 224 shows the arrangement of such a system. 
In this case the hot-air furnace supplies heat to the lower floors 
and the hot-water circulating system to the upper floor. 

Any system of piping suitable for hot-water heating can be 
employed for this purpose: the one shown is that of the com- 
plete-circuit or one-pipe system, the heated water being taken 
directly to the top of the building and all radiating surface 
supplied by the descending current. As the writer knows 
from experience, it is very difficult indeed to proportion the 




Fig. 224. — Combination System, Hot-air Furnace and Hot Water. 



heating surface in the furnace and the radiating surface in the 
room so as to give in all cases satisfactory results without an 
irregular and uncertain distribution of heat. It will generally 
be found that the fire maintained in a hot-air furnace is much 
more intense than that in a steam or hot- water heater; and 
further, the heating surface which is usually employed is sub- 
jected to the full heat of the fire, consequently a smaller 
amount of heating in proportion to radiating surface must be 
employed. Whereas in the ordinary hot-water heater one foot 
of heating surface supplies from 8 to 10 of radiating surface, 



afi HKATDCG AXD VKNTILATIXG. 

iT3 ihi? sj^stem i foot of heating suriaoe wiH supply ^5 to 35 fen 
of Titduiing surface in coal-biimzDg fumaoes a&d 50 to 75 in 

wood-biaminxr furmuxs, 

Siznikj comlonatian 5}^stem5 otf bol 221 £zd steam jme also 
usfvi, bui in >uch cases ibe beater ninst be very madi like a 
sTTjim-boiicr, and possess aJI its applHancses and also storage 
r.afia4."an for sicam. In ibe case of ibe bol-'«rater aikd hot-air 
s\'jaxan the beaiei is substanlialh' a bol-air fnmafy. to mikh is 
iiddcd a a-al of pipie or vessel of suitaiile iorm. -idiidi acmes as 
xhi' bwiXiiip suriax:^- for lie bcu vaier. so thai lie chaiige in 
cansarurucin is >'iirv- siixrhi; bul icn sLeam-ieanng lie riiangc 
of vViTisiTuriiori irus: bf Tnore maited, and is Tit eh' to be more 
C3cpf»n?d\'r ano romTiiicaixd. 



CHAPTER XIII. 
HEATING WITH HOT AIR. 

156. General Principles. — The general laws which apply to 
hot-air heating have previously been considered in the articles 
relating to "Ventilation" and to the "Methods of Indirect 
Heating with Steam or Hot Water." The method of heating 
with hot air, as usually practised, consists in first enclosing a 
suitable heater, termed a furnace, in a small chamber with brick 
or metallic walls, which is connected to the external air by a 
flue leading to its lower portion and to the various rooms to 
be heated by smaller flues leading from the upper part. In 
operation the cold air is drawn from the outside, is warmed by 
coming in contact with the heated surfaces of the furnace, and 
is discharged through the proper flues or pipes to the various 
rooms. The rapidity of circulation depends entirely upon the 
temperature to which the air is heated and the height of the 
flue through which it passes. In order that a system of circu- 
lation may be complete flues must be provided for the escape 
of the cooler air from the room to be heated, otherwise the 
circulation will be very uncertain and the heating quite imsatis- 
factory. Registers and flues for the escape of the air from the 
room are often neglected, although fully equal in importance to 
those leading to the furnace. 

Regarding the relative merits of hot-air heating by furnace 
as described and of the various systems of steam or hot-water 
heating, little can be said in a general way, since so much 
depends on circumstances and local conditions. It is rarely 
that these systems come in direct competition. The force 
which causes the circulation of the heated air is a comparatively 
feeble one and may be entirely overcome by a heavy wind; 

327 



328 HEATING AXD VEXTILATKG. 

consequently it is generally found that the horizontal distance 
to which heated air will travd under all conditians is short; 
hence the s>'5tem is in general not well adapted for large 
buildings. When properly erected and weU proportioDed, this 
system gives, in buildings of moderate size, ver>' satisfactcny 
results. 

It may be said, howe\'er, that, in erecting a hot-air system 
of heating, competition has been in many cases so sharp as 
to induce cheap, rather than good, construction. Small fur- 
naces have been used in which the temperature of the erterior 
shell had to be kept so high, in order to meet the demands for 
heat, that the heated air absorbed noxious gases from the 
furnace and entered the room in such condition as to impair, 
rather than to improve, the ventilation. Ventilation-ducts 
for removing the air from the rooms have often been n^lected, 
and hence the results obtained have been far from satisfactory. 
Such faults are to be considered, however, as those of design 
and construction rather than as pertaining to the sj'stem 
itself. 

In order that the hot-air system should be satisfactory in 
every respect, the furnace should be sufficiently lai^e, and the 
ratio of heating surface to grate such that a large quantity of 
air may be heated a comparatively small amount rather than 
that a small quantity shall be heated a great amoimt. As 
air takes up heat ver>' much more slowly than steam or water, 
it would seem that the relative ratio of heating surface to 
grate surface should be more than that commonly employed 
in steam-heating. By studying the proportions which have 
previously been given for steam-heating boilers it will be seen 
that the ratio of heating surface to grate surface for the steam- 
boiler varies between 20 and 45, averaging about ^2, From 
a study of the results in catalogues of manufacturers of furnaces 
the ratio of air-heating surface to grate surface in hot-air 
furnaces seems to var>^ from 20 to 50 as extremes. These pro- 
portions are essentially the same as used in steam-heating 
and arc much too small for the best results in hot-air heating. 
It is quite evident that since air cannot be heated by radiation. 



HEATING WITH HOT AIR. 329 

and is warmed only by the contact of its particles against the 
heated surface, that the exterior form of the furnace should be 
such as will induce a current of air to impinge in some por- 
tion of its course directly against the surface. 

Regarding the economy of this or any other system of indirect 
heating, it is simply a question of perfect combustion and rela- 
tive wastes of heat. If the fuel is perfectly burned and all the 
heat which is given off is usefully applied, the system is per- 
fect. The waste of heat in any system of combustion is that 
due to loss in the ashes, to radiation, and to escape of hot 
gases into the chimney. If the furnace is properly encased 
and if the hot-air pipes are well covered, there is no reason 
why losses from imperfect combustion and from radiation 
should not be a minimiun. The chimney loss depends largely 
upon the temperature of the surface of the heater; if this is 
high, the loss will be large. In general, it may be said that 
the larger the heating surface provided the lower may be its 
temperature, and the greater the economy. It should be 
noted, however, that this or any system of indirect heating 
requires the consumption of more fuel than when the heating 
surfaces are placed directly in the room, and for that reason 
the operating expense must be considerably greater than that 
of direct systems of hot-water and steam heating. 

Furnaces, or in fact heating-boilers of any kind, are xmeconom- 
ical if operated with a deficient supply of air. In this case 
the product of combustion will contain carbon monoxide, 
an extremely poisonous and inflammable gas, which is quite 
likely to take fire and bum, on coming in contact with air, at 
the base or top of the chimney. 

157. General Form of a Furnace. — The principles which 
apply in furnace construction are not essentially different 
from those given in Chapter VIII for steam and hot-water 
boilers. In the case of a hot-air furnace the fire and heated 
products of combustion are on one side of the shell and the 
air to be warmed on the other. In the case of steam or hot- 
water boilers the water and steam occupy the same relative 
positions as the air in the case of the hot-air furnaces. The 



aw HEATI5G AXD VEXlILATiyG. 

typ^ ^A Ujttta 'A iumiicts wliich are in use may be H3i«ifi#wi 
e»i/.i]y t^MT i!iSime a» heating-boilers, as having (dain or extended 
wri^j:^ ari/1 ai^ being hfmzAmXzH or vertical, tubular ch* sectional; 
ft r^;ay tx; i^ai/l that the forms which are in use are fully as 
mitn^'AXh a» thotie described for steam-heating and hot-water 
fiiirating. 

7 he material which is employed in construction is usually 
raa^t ifm or htcel, and there is a ver>' great difference of <^ini<xi 
tt3> Ut the relative merits of the two. It seems quite probable 
that ciitsi iron, l>c*cause of its rough surface, may be a better 
mirdium for giving off heat than wrought iron or steel, but it 
U r|uite certain that at a very high temperatiure, some carbon 
from the caHt iron will unite with the oxygen from the air 
forming (;arlK)nic acid. When very hot it may be slightly 
permeable to the furnace gases. Such objections are, how- 
ever, of little practical importance, since the temperature of a 
furnace never should, and never does if properly proportioned, 
exceed 300 or 400 degrees Fahr., and for this condition the 
(lilTcTcncc in heating ix)wcr of cast iron and steel is very 
ftlight. It is of great importance that the shell of the furnace 
he tiglit, HO that smoke and the products of combustion can- 
not enter the air-passages. 

Furnaces can l)e purchased with or without magazine feed, 
l)Ut the demand of late years is principally for those without 
the magazine, since it has not been proved to present any 
special advantages. 

I'urnacos arc often set in a chamber surrounded with bride 
walls, as explained for steam-boilers, but they are more fre- 
(juently sc^t inside a metallic casing, this latter being termed a 
I>ortal>lo sotting; this casing varies somewhat as constructed 
by dilTcMont makers, but usually consists of two sheets of metal, 
th(^ out(M- of gaKanizcil iron, with intervening air-si>ace empty or 
\\\\i\\ with asl>ostos. The casing is placed at such a distance 
irom the furnaoo a.^ to provide ample room for the passage of 
air. 

Some ioni-j of vlunipinc v>r shaking grate which can be 
roa*iil\ anvl i^^i^^kK ^loanoti is almost invariably onployttl 



HEATING WITH HOT AIR. 331 

The draft-doors which admit air below the grate and check- 
dampers in the stovepipe are usually arranged so they can be 
oi>ened or closed from some convenient place on the first floor 
of the house by means of chains passing over guide-pulleys. 

A pan in which water may be kept is added to every fur- 
nace for the purpose of increasing the moisture in the air; 
this is of importance, since the heated air requires more 
moisture than cold to maintain a comfortable degree of satur- 
tion. 

158. Proportions Required for Furnace Heating. — The pro- 
portion of the area of heating surface in the furnace to that 
of the grate cannot be computed from any data accessible to 
the writer, and the proportions given are assumed to be twice 
those which have been found to give best results in steam-heat- 
ing; these apparently agree well with the best practice.* The 
tables which are given are computed for a maximum tem- 
perature of 120° F. for the air leaving the furnace, which is 50 
degrees in excess of the ordinary temperature in the house. 
No doubt better practice might require the introduction of 
more air at a lower temperature, but considering the fact that 
this high temperature only has to be maintained when the 
outside weather is extremely cold, it seems quite doubtful if 
the expense of a furnace large enough for this additional duty, 
would be warranted. 

The ratio which the grate surface of the furnace should bear 
to the glass and exposed wall surface of the room can be com- 
puted with suflBcient accuracy from known data relating to the 
heat contained in coal and to the probable eflBciency of com- 
bustion. The heat given off from the walls of a room for each 
degree difference of temperature between the inside and out- 
side is approximately equal to the area of the glass plus one- 
quarter the area of the exposed wall surface, which we will 
in this place denominate as the equivalent glass surface. One 
pound of good anthracite coal will give off about 13,000 heat- 

♦ The Federal Furnace League find average values of i sq. ft. of direct heating 
surface and 1.5 sq. ft. of indirect heating surface or a total of 2.5 sq. ft. of heating 
fiuzfoce per square foot of grate surface. 



332 HEATING AND VENTILATING. 

units in combustion. One pound of soft or bituminous coal 
will give off in combustion from 10,000 to 15,000 heat-units, 
depending on the kind and quality. Of this amoimt a good 
furnace should utilize 70 per cent.* The amount of coal 
which is burned per square foot of grate surface per hour will 
depend very much upon the character of attendance; in 
ordinary furnaces used in house heating, and where it is ex- 
pected to replenish the fires only two or three times per day, 
this amount is low, being not greatly in excess of 3 pounds. 
If the air is 120 degrees in temperature, nearly 60 cubic feet 
will be required, when heated one degree, to absorb one heat- 
unit (see Table X), and if such air is delivered 50 degrees above 
that of the air in the room, each cubic foot will bring in f of one 
heat-unit. 

The velocity of air in feet per minute with ample allowance 
for friction is given in Appendix, Table XVI, from which it is 
seen that it will be safe to assume velocities of 4, 5, and 6 feet 
respectively, per second in the flues or stacks leading to the 
various floors. The velocity of the air passing the register 
may be assumed as 3 feet per second in every case; this 
lower velocity is obtained by making the area of the register 
somewhat larger than that of the pipe leading to it. 

• The following mathematical discussion gives these various consid- 
erations in general and algebraic terms, as follows: 

Let F= square feet in grate, C= weight of coal burned per square 
foot of grate per hour, r= heat-units per pound of coal, £= efficiency 
of furnace, A= heat-units per hour, 7"= temperature of air leaving fur- 
nace, /' = temperature outside air, / = temperature of room. G=area of 
glass in room, IF = area of exposed wall surface, H=hcat lost by room 
for one degree difference of temperature, A^= cubic feet of air heated by 
furnace per hour, /iL' = cubic feet air required to warm room. 

We have, as explained, 

h=CFEr =ioi3\ heat given off by furnace, equal to that required for 

all the rooms (i) 

* It is quite probable that the cflTicicncy of combustion in an ordinary furnace 
is much less than the above, often as low a^ 50 per cent. 



HEATING WITH HOT AIR. 333 

K=— — 7-= cubic feet of air heated per hour by furnace. ... (2) 
A'=(G-fiW)(/—/') = total heat-units to warm the room (3) 

K = — = cubic feet of air to warm the room. ... (4) 

J, ^~ * 

For average conditions substitute in above, as explained, r=i20, 
^=70, /'=o, C=.7o, r= 13,000, Cr= 9100, and we have 

h = giooCF=2K (5) 

A'=455oCF=o.5// (6) 

/i:' = 84(C+iin (7) 

yNhtnK=K\ CF=—-^; when C=3, F=^4^?-' (8) 

54.2 162.6 

A'=7o(G+JPr) (9) 

For computing areas of leader-pipes and stacks, for resi- 
dence heating, assume velocities which can safely be taken as 
follows: First floor, 4 feet per second or 240 per minute; 
second floor, 5 feet per second or 300 per minute; third floor, 
6 feet per second or 360 per minute. 

Through a cross-section of the flue equal to one square 
inch 100 cubic feet will pass in one hour when the velocity is 
4 feet per second, 125 when the velocity is 5 feet per second, 
150 when the velocity is 6 feet i>er second, 251; when the velocity 
in feet per second is represented by v. 

Denote area of flue in square inches by L; then from equa- 
tion (7) 

252; 251; V 

From this, by transposition, we have 



334 



HEATING AND VENTILATING. 



If for first-floor rooms ?=4 



G+\W = i,igL. 



If for second-floor rooms r = 5 



If for third-floor rooms r = 6 

G-fjH' = i.78L. 

The following table gives the relative values of these vari- 
ous quantities, computed for the conditions as explained: 



PROPORTIONS REQUIRED IX FURNACE HEATING. 



1 



Equivalent glass surface 
Cu. ft. air to be heated 

per hour 2100 

Grate area, square inches 22 
Equivalent diameter 

round grate, inches. . . 7.5 
Heating surface, sq.ft . . 4 

Diam. smoke- pipe, ins 

Approximate cubic feet 

space 
Area stack: 

1st floor (vel. 4) sq.in 

2d *• (vel. s) sqin 

3d " (vel. 6) sq.in 
Diameter leader pipe: * 

1st floor 

2d '• 

,3d *• 

Net area, register, sq.in. 

xst floor (vel. 3) 

2d floor and above. . . . 
Area ventilating flue 
Net area ventilating 

register 



25 SO 



i .. u 



I d 



!00 125 



ISO 



I 



4.200 6300 8400 



43 I 04 
6 . 8 



8S 

I 

11.5 
10 



10500 
107 

12 5 
12 



12600 

127 I 

13.5 
IS ! 



420 
52s 

21 
17 
14 



42 
33 

28 



I : 



28 
21 
21 



840 1260 1680 
1050,1570.2100 

84 ' 

08 
55 

10.5 
OS 

8.5 



63 
SI 
42 



7-5 9 

7 |8.2 

mm ^ * 



56 
42 
42 



84 no 
63 84 
63 84 



17 33 ' 51 68 



2100 
2625 

105 
85 
70 

II. 6 

10.5 

9.5 

210 , 



105 
105 I 



2520 
3150 

126 

102 

84 

12.7 
II. 5 
10.4 . 

168 
126 
126 



200 

16800 
170 

IS 
22 

336 
4200 

If.S 

135 
I 12 

14. T 
13- 2 
12 

I 

224 

lf)S 
168 



250 500 750 ■ 1000 
I ! 

21000 42000 63000 S4000 
212 ' 425 640 850 



85 102 I 135 



17 
27 

42 o 

5250 

210 
170 
140 

16.5 

14.7 
13.4 

280 
210 

210 

170 



*4 29 33 

53 So 100 

8 10 IE 

8400 12600 l6<oo 

2100 15750 21000 

' ^-- ' 840 



420 I 630 



345 

280 



500 
420 



19 I 23.2 

21 I 25.2 
19 23.2 

560 840 
420 , 630 
420 630 



670 
560 

26 7 
29.2 
26.7 

II20 
840 
840 



345 500 670 



♦ For pitch of one inch per foot. Use larger pipe for less pitch. 

Note. — The proix>riions in the above table agree vcr>- well with those given 
by the Excelsior Steel Furnace Co. for the condition of changing the air in each 
room four timers p)er hour, which can be taken as representing the average amount 
required to bring in the heat. 

The grate surface is computed for combustion of 3 pounds per square foot 
per liour. uiili an ctiu ieiuy nf 70 jkt cent or a greater amount at less eflicieno*. 
The hciilini: -^uria' i- L'i\in in abnvc table is much larger than ordinarily found 
in furnat 0. but nut ini» larjc for best results. 



HEATING WITH HOT AIR. 335 

159. Air-suH»ly for tbe Fumace. — The air-supply for the 
furnace is usually obtained by the construction of a passage- 
way or duct of wood, metal, or masonry leading from a point 
beneath the furnace casing or near its bottom to the outside 
air, essentially as shown in section Fig. 225. This duct or pipe 
is usually termed the cold-air box and is often constructed of 
wood. In all cases there should be a screen over the outer 
end to keep out vegetable matter or vennin, and doors should 
be arranged so that it can be cleaned periodically. A damper 
is usually desirable, arranged so that it can be partly or entirely 
opened to regulate the admission of the cold air. The cold- 
air box should be made perfectly tight and in a workmanlike 




tjT 



Fic. 135.— Hot-dr Furnace with 0)ld-dr Bm below Cellar Bottom. 

manner, so that air cannot escape into or be drawn from the 
cellar or basement. This should join onto the furnace casing 
at as low a point as the character of the cellar bottom will per- 
mit. In some instances it is desirable to erect two cold-air 
boxes, opening to the air on opposite sides of the house, so 
that the supply may be drawn from either direction as required 
to obtam the help of wind-pressure, to aid in the circulation 
of the air over the furnace. 

The cross-sectional area of the cold-air box is proportioned, 
by different authorities, from 66 to 100 per cent of the sum of 
the areas of all pipes taken from the fumace. If tiiis were 
proportioned so that its area should be in ratio to the respective 
volume of cold and heated air, the sectional area of the cold- 
air box should be about 80 per cent of the sum of the areas of 
the various stacks. To avoid frictional resistances it would 



336 HEATING AND VENTILATING. 

seem to be advisable when practicable to make its area equal 
to that of the sum of the areas of the stacks. 

i6o. Pipes for Heated Air. — The pipes for heated air aie 
of two classes; first, those which are nearly horizontal and are 
taken from near the top of the furnace casing — these are usually 
round and made of a single thickness of bright tin, and if 
possible erected with an ascending pitch of one inch to one 
foot, and are termed leader- pipes; second, rectangiilar verti- 
cal pijws or risers, termed stacks, made m such di m ens io ns as 
wilt fit in the partitions of a building and to which the leader- 
pi^K' connects. The bottom of the stack is enlarged into a 



VV. .■.■". -Konstifc Sons :%>wTi in pDsCitD. 

vhsimlvr tcritio.1 a iwt, wluch is made in %-arious f<»ms and pro- 
vivUxl with A n.>i,uKl i.vUa.r for cotmectioD to the leada-pqjC^ 
The tk,'(> i>ar( v'l the stack, may bt pn.'vided with a amilar boot 
itviii which h-,'ruv'nt,il r^vtan-r-itor :Jtacks ore tiken. or it may 
bv ',vmt<,vti,\t li." a n.vtari;;uUr chan-.ber into which the renter 
i»ia> K- iilU\t .i:k1 which is k.-;owti li the noisier box. The 
ttack^ i,!-ii;,i!i\ !Mss •..;;> cr rrcxr :!.■:'; wt.'c^iwork. of partitions. 
a^n! !.•( vw,-H"-.; !.:\- ^vv -■^A .IS wi:" 05 rreMJCtiiig loss of heat 
v.Vi,;'<,i \- ■■Mvk' w.'> sV,>ic «-,i"s •icfMrj.U'ii by aa intervening 
.(■:-.n;sivv I'v ■v:;--".," "i-Vv-i vw'o ji'.*.' "^ tf^Tjry case ha« 
v'\-i"'\- ^w"■, •■'v ;i.-.>v-ii' ■.-)■-■ .-. ,1 5:aci in positioa itt t 
!M' -•■■ vi> ' \-,>: I : i,^,-.- !■. '.\'t:vi" ■,-- ".<jj.'iKr-pipe and with 
?v-. ••■ ,-■■ -vv . .-.■ ■■.■■-■..■.■. '\-.\, -s >;i»-w-i Li :he accouqiatty- 



^^^^^P HOT ^^M 


The leader-pipes and stacks, boots, and register boxes are ^^H 


now a standard article of manufacture by several firms. ^^H 


It will be found profitable in nearly every case to wrap the ^^H 


leader-pipes with two or more thicknesses of asbestos paper ^^H 


and mineral wool in order to prevent loss ^^H 


of heat. It is desirable to locate the stacks ^ 


9*1 


in the inside partition-walls of the building, Hj 


■9 


or where they will be protected as much as m 


mm g 


possible from loss of heat, since any loss ill 




affects the rapidity of circulation. It is '■ 


.'i^i'l " 


generally necessary to have the leader -pipes 


''''1 Z 


not over 15 feet in length, otherwise the 


— Ji i 


circulation will be uncertain In amount and 


^ 


character. ^ 
In a test at the Underwriters Labora- , 


► 1 


1 


tories, Chicago,* W. C. Robinson, Chief En- F 


1 


gineer, shows that the outer wall of the ' 


J 


double wall stacks gets only about 75 to 80 !j, 


H 


per cent as hot as the wall of the single 


" 


stack. The asbestos cover on the single wall 


2 


stack affords very little protection. '; 


a 


" One of the vital points involved in these - - 


-^ i 


tests has been to demonstrate the greater ' . ,. 
efficiency of double wall pipe of smaller area 


»s 


i 


in comparison with single wall pipe of larger i:_ 




area, the single pipe installed in the wall in 


1 


question being 3&X12I, whereas the double 




pipe had a cross area of only 3X12 inches, l| 


d 


Notwithstanding an increased area of more ^^F 


"^■= 


than 25 per cent in favor of single pipe the |p| 1: ', |^ ^^M 


latter showed much less efficiency than double IJ,,': _^^ ^^M 


wall pipe, due to the very great loss of heat ^^B 


into partitions with single pipe. The area of the double pipe ^^M 


tested was 56 square inches, and of the single pipe 45^ square ^^M 


inches." ^^| 


^^^^^^^k * From the Engineering Review. August, ^^^H 



338 



HEATING AND VESTXLATING. 



The inclined or baseboard register, see Fig. 228, for use on 
the first ston' of a house is not a receptacle for dust like the 
flat floor register. 




HEATING WITH HOT AIR. 



339 



i6i. The Areas of Registers or Openings into Various Rooms. — 

Registers are made regularly in various forms, square or round, 
and arranged for use either in the floor or side walls as required. 

TABLE OF SIZES AND DIMENSIONS OF SAFETY DOUBLE HOT- 
AIR STACKS* 











1^ 


5 


-S 


fi 


§^ 


-gl-^d 


g^ 


J 


= 


I 


1 


1 


IS 


il 


K 




■sP 


Kl 


1! 


1 


■3 
S 

m 
1- 
1 


1 

■3 

1 

1 


1 

< 


m 


1 




i 
31 


1 

I 




■sg 


1 


4XS 


X , 




U 


M 


JS^ 


** 




i! 


^Tx 


81 soo 


6X 8 


3S 


:«■! 


s,s 




3»1 


48 


H 






sx 


)■ iSoo 


IxW 


41 

ss 












ai 












60 


!5l! 


§ 




fi 


47 


?? 






*: 


loX 


I «JS 


-X[4 




6X11 






ss 
















,:; 


exi. 






XiJ 


6S 












7 1600 






6X>6 
















IS4 








155 


BXl8; 


SSIJ 






"4 






















Sio 


.J6 


164 
















iaX3t'MX:i3l\9iXii 






"" 




^^ 


aiX 


7P00 


JOXJS 


"° 



• Thil tible it copyriahlid by Eicel^or St«l Fufomee Co. 

These registers are usually supplied with a series of valves 
which may be readily opened or closed. The space taken by 
the screen and valves is usually about J of that of the register, 
so that the effective or net area is about \ of the nominal ^ze 
of opening. These registers may be obtained finished in black 
or white japan, or electroplated with nickel, brass, bronze, or 
copper. The table on page 340 gives the various sizes of 
registers which are regularly on the market, their effective area 
in square inches, and diameters of round pipe having the same 
capacity. 

The areas of stacks may be considerably less than those 
of the registers, since it is generally required that the velocity 
of air entering the room shall not exceed 3 or 4 feet per second, 
while that passing through pipes and stacks may have the 



340 



HEATING AND VENTILATING. 



highest velocity possible, which for the different floors wiD 
not differ greatly from 4 to 6 feet per second, as already explained. 



TABLE OF REGISTERS. 





ElJ*ctiv« 


I 
Diameter 
Round E>ip«.' 
Inches. 


Sire of 
Opearn^. 

Inch**. 


EffectiT* 

Ax«a. Square 

laches. 


Diameter 
Round Pipe. 
Inches. 


4|\ Oj 


-•0 


5 


I 


loX^ 


li- 


13 


4 \ S 


^l 


5 


» 


i2Xr^ 


QO 


II. I 


4 \tO 


X» 


5 


S 


i-Xu 


112 


II 9 


4 X-^.^ 


.U 


c 





11X15 


120 


12.4 


4\:5 


40 


1* 


% 


liXlO 


IlS 


12 8 


4\t5 


45 


• 


$ 


I -• X I • 


130 


13^ 


.-'X 


:4 







i-'Xi5 


LU 


13 5 


CX 5 


• * 




4 


i.:\ ig 


15- 


13 9 


.^X 




:> 


■•^ 


i;X re 


rc» 


M 3 


-^ X :c 


4C 


" 


♦ 


i;\ ii 


102 


15-6 


-^Xu 


50 


5 


% 


14'* 14 


150 


12 S 


^X;.- 


^4 




fc 


:aX:? 


140 


14 s 


•X;5 






% 


i4.X:5 


i-^ 


14 7 


^X:a 


>.V 






:aX :c 


i5c 


15 


« 

^ 


•X ' 


• * 


* 
^ 


4 


:a\ i: 


2C5 


10 


* 


-X-." 




> 


» 
•• 


15X25 


-5= 


17 


3 


sx > 


*: 


^ 


4 


:?\ :: 


i-c 


14 


1 


>X ." 


*.i 




» 


:? \ ^^ 


* • • 


10 


5 


S\ • 






% 


:r\ :^ 


2?C 


iS 


X 


>X X 


x- 


■>:• 


^ 




2ii* 


IQ 


2 


S\ < 


>>* 


■ 


» 


.-ex .-vr 


2C"* 


xS 


m 

3 


,X V 


■»-« 


X 


.- 


V N :♦ 


52c 


20 2 


vX 


« 1^ 


« 


% 


"C N r-i 


54* 


21 


. \ . 


•N 


• * 


^ 
^ 


• ^ ^^ 


.cc 


» » • 


,\ . 


N 


^ 
^ 


% 


. ^ * 


r^ 


22 I 


, \ 


S' 


^ 




• ^ ^ r 


5: 2 


^5 5 


.-\ 


V* 


* 




- * \ ; ' 


Ix- 


25.0 


-\ * 


%.^ 


^ 
•* 


* 


• " V .'^ 


"^4 


^ 5 


. \ » 


% 
^ 




^ 


,.'' '. -C 


'CC 


• « 4 


, \ ^ 


V 




« 









X ^ X 






X .« - 



■ * X 



X. 



. \ . 



V X 



X5 r.^ I2tf reiam'e 
^ Ti^Tx^e?^ I: is 
. r r:.:sc rvvcs on 
.* ~b^' >ec-"co And 
^\ •c'i! fx'm JLnd 
■■ \.-. ^::n; nr^dily 

. ^ ::r ^*,isC Jsd 



HEATING WITH HOT AIR. 341 

sweepings of the room and in a position to materially interfere 
with the carpets. It will be found that the experiments made 
by Briggs as to diffusion of air hold in the case of furnace heat- 
ing the same as in that of any other system. From these experi- 
ments it would seem that the highest eflBciency would be attained 
when the inlet for the heated air was at the side near the top of 
the room and the outlet for ventilation near the floor. This 
distribution is one that, so far as the writer knows, has never 
been practised in furnace heating of residences, although it 
is the commonly accepted method in school-house heating, 
whether with a furnace or an indirect system of steam or hot- 
water heating. 

162. Circulating Systems of Hot Air. — By connecting the 
cold-air box with the hall floor or the lower portion of a pas- 
sage communicating with all rooms of the building and clos- 
ing outside connections a downward current of air will pass 
from the rooms to the furnace, which, being warmer than the 
outside air, will aid materially in heating. Such a connection, 
if properly made and used with judgment may be of great 
service in reducing the cost of operation without seriously 
affecting the ventilation. Such a system if erected, however, 
should be supplied with devices to prevent overheating and 
arranged so that cold air can be drawn from outside of the 
building whenever desired. There is so much danger that 
ventilation will be poor with this system that it is not recom- 
mended. 

163. Heating with Stoves and Fireplaces. — The manufacture 
of stoves for heating purposes is a very great industry in the 
United States and they are extensively used in the cheaper 
classes of dwellings. In every case the stove is located directly 
in the room to be heated and is connected with a chimney 
by means of several lengths of sheet-iron pipe. Stoves are 
built in many forms, some of which are very elaborate and 
highly ornamented, and in many cases they are provided with 
magazines from which the coal feeds itself automatically as 
required. The heat given off from a stove is generally nearly 
all utilized in warming, perhaps not over icons per cent being 



342 HEATING AND VENTILATING. 

carried off by the chimney. Stoves do not, however, present 
an economical mode of heating, largely because the wastes which 
occur from the operation of small fires are very great and 
cannot be avoided. It is doubtful if the efficiency averages 
much above 25 per cent. In addition, the stove occupies 
useful room, is the source of very much dirt and litter, and 
requires a great deal of attention. 

Open fireplaces which were used at one time extensively 
are very wasteful, as little more than the direct radiant heat 
from the fire is absorbed in warming. They are also subject 
to all the wastes which pertain to stoves, and their probable 
efficiency cannot be considered as over 15 or 20 per cent. 
They are, however, valuable adjuncts of a system of ventila- 
tion, since large quantities of air are drawn from the room and 
discharged into the chinmey. In the use of a stove called a 
fireplace heater, the heated gases from an open fire pass through 
a dnun or radiating surface in the room above, and the heat 
which otherwise would be discharged from the chimney and 
wasted is partly utilized in heating. 

164. General Directions for Operating a Furnace. — ^The gen- 
eral directions for operating a furnace so far as regards the 
care of the fire are the same as those which have been prev- 
iously given for the operation of steam-heating furnaces; there 
are, however, no steam-gauges or safety appliances needed 
In regulating the temperature of the house the drafts of the 
furnace should be operated rather than the valves of registers 
leading to various rooms. In some instances, if the circula- 
tion is strong in certain directions and weak in others so that 
certain rooms cannot be heated, it may be a good plan to 
shut all registers except the one to the room where heat is 
required until circulation is established, after which circulation 
will usually continue without further attention. In the opera- 
tion of a furnace great care should be taken that the metal 
never becomes red hot or even cherry-red. If it will not warm 
the building without being excessively hot, the furnace is too 
small, or else has too little radiating surface in proportion to 
the fire-pot. The water-pan should be kept filled with water. 



HEATING WITH HOT AIR. 



S43 



Thennostats arranged to open or close the drafts when desired 
are in use in many systems of furnace heating with success. 

For protection of the furnace during summer months some 
makers recommend that the fire-pot be filled with lime. For 
burning soft coal, furnaces of special construction only should 
be employed. 

165. Practical Ammgement of Furnaces. — Furnaces arc 
usually arranged in an approximately central position with 
reference to the rooms to be heated, although the location 
must in a large measure depend upon the position of the chim- 
ney. The cold-air flue or box is arranged as convenient and 




Fig. itg.—Ekvn 



SO as to enter the furnace either below or above the level of 
the floor, and to secure best results this box should open on 
the windward side of the house so that the force of the wiiid 
may be utilized as far as possible in producing circulation. 
In localities where the winds often vary in direction it is 
advisable to erect, when possible, two cold-air flues, so arranged 
that the one which produces the better results can be used and 
the other closed off by a damper. 

The hot-air pipes are almost universally taken off from the 
top part of the hot-air chamber and at the same level, and 
erected without branches, so that we find as many pipes in 
use as there are rooms to be heated. 



344 



HEATING AND VENTILATING. 



The usual arrangement of cold- and hot-air piping is shown 
in the accompanying figure. In this particular case the 
cold-air box is upon the floor, the furnace has a portable setting, 
and the hot-air pipes are taken from the top of the hot-air 

• 

chamber. In a few instances partitions or pipes in the hot- 
air chamber are arranged so that a definite area of the furnace 
surface is used to warm the air for each hot-air pipe, it being 
expected to produce by such a construction a more positive 
flow of air to the remote rooms. It is doubtful, however, 
if the heating is more reliable than that which can be obtained 




Fig. 230. — Plan and Elevation of Furnace with Main Pipe and Branches. 

• ■ 

with good proportions of parts when arranged in the usi^al 
manner. 

In the opinion of the author the hot air could be distrib- 
uted with much less friction were a system of main pipes 
and branches employed as suggested in the diagram Fig. 230. 
If the friction in the distributing pipes could be entirely elim- 
inated, the trouble which is now experienced in securing the 
circulation of hot air to remote rooms would cease almost entirely 
IncidenUilly, this system of piping has the advantage of taking 
less room in the cellar and is doubtless cheaper to construct. 



HEATING WITH HOT AIR. 



345 



The figure shows the pipe-line extending only in one direction, 
but it is evident it could be equally as well extended in two 
directions. In proportioning such a pipe-line, first find the area 
of branches, then of submain, and lastly of the main. 

The hot-air furnace is rarely used for ventilation purposes 
during that portion of the year when little or no heat is required. 
It is possible, however, to arrange the furnace so as to deliver 
a constant volume of air durii^ the entire period of its use, 




Fig. 131.— Ventilating-pipes used at Furnace. 



as suggested in the sketch Fig. 232. In this case a by-pass 
pipe connects the cold-air box with each hot-air pipe; at the 
point of junction, as at Z7, a damper is placed, which is so 
constructed that as one pipe is closed the other will be opened 
an equal amount, thus delivering a constant volume of air 
into the room, which may thus be had hot or cold or at any 
desired temperature, as required by the occupants. 

Vent-pipes having 80 per cent of the area of the hot-air 
pipe, and provided with registers, should be built in the par- 
titions, and should connect each room at a point near the 
floor with the attic or outside air, in order to permit the escape 
of a volume of air equal to that brought in by the furnace 
with as little resistance as possible. 

Approved methods of setting floor- and wall-registers are 
shown in detail in Fig. 232, the same letters being used as 
far as possible to denote the same object in each view. The 



346 HEATING AND VEXTILATIXG. 

end of the vertical [npe above the wall-register diould be curved 
so as to direct the entering air through the register. 




Fig. J32.— Detaik of Flout- Mid Wall-regislCTs. 



166. The Federal Furnace League rates hot-air furnaces 
as to capacity only by actual testing in square feet of equivalent 
glass surface by the use of the following rules,* 

To find heating requirements for each room: Compute the 
number of square feet of glass exposure, and 

For north north-west and west glass exposure, add 20% 

For north-cast glass exposure, add 10% 

For cast and south-west glass exposure, add nothing 

For south glass exposure, deduct 20% 

For south-east glass exposure, deduct 10% 

" Copyrighled by the Federal Furnace League. 



HEATING WITH HOT AIR. 347 

To the total allowance for glass exposure as figured by fore- 
going method: Add one-sixth of the number of square feet 
of net wall exposure. 

To be counted as regular single glass exposure: 

Outside doors (not vestibyled). 
Ordinary single windows. 
Skylights (single). 

To be counted as 50 per cent (50%) of regular single glass 
exposure : 

Outside door (vestibuled). 
Double windows. 
Windows fitted with storm sash. 
• Double skylights. 

The percentage additions to and subtraction from glass 
exposure, are based on the following maximum wind velocities: 

North wind blowing 25 miles per hour, add 20% 

West wind blowing 25 miles per hour, add 20% 

East wind blowing 15 miles per hour, add nothing 

South wind blowing 5 miles per hour, deduct . 20% 

In some localities where extraordinary wind velocities are 
quite common, the following percentages may be added to glass 
exposures: 

Wind blowing 35 miles per hour, add 40% 

Wind blowing 45 miles per hour, add 60% 

To be counted as net wall exposure: 

Actual number of square feet of outside wall surface. 
Floor and ceiling of overhanging bay windows. 

To be counted as 50 per cent (50%) of net wall exposure: 

Party walls. 

Partitions (including doors) between heated and cold 
rooms. 

When the walls of a building are of concrete add one-fourth 
(J) of the number of square feet of net exposed wall surface 
{instead of one-sixth (|)]. 



HEATING AND VENTILATING. 



PROPORTIONS m 



■„"S 


E 

1 
1 


1 


•s 

1 


! 

3 


1 


= 

1 
1 

I 
11 


ii 

1 


1 

8 

1 

1 

z 


i 


Reported by W 
J. Woodall. 
fcoraelUville. 
Pa. SWre and 
Kjidence. 


Dia. Ar. 


^t' 


buck-li"ed; 
fire- pot. 


Tom. 


Cu. (t 


ii 


aj. It. 






Reported bvW 
Pa. Church. 


-■;.?■' 


" 


Do. 




.,.»0 


i8Xi,kii 


3510 


1-6x14 

1-8X8 


" 




-546' 


„ 


Do. 




...... 


■ir 


4h8^ 


"it 


.» 




,.■..„ 


US 


Ca« iron; 
b"; jacket. 


P 


1 .-..„ 

1 balloon- 


4)-6;5 




... 


't'^K'ifiV.V 

Wilkesbarre. 

AdjoininH^a'' 
Sunday-school 
at one end. 


JO" 706 


.. 


Do. 


1 


1 Auditorium 
1 balcony 

1 


4)3 TOO 


4X11 


440 


irsv 


10" 400 


1 
= 


ironi'^i^di- 
rect draft. 
Inside tast- 
ing: 18? Car 


,.s ,....,1 S!| 


11IT0 


■■ 


lift 



HEATING WITH HOT AIR. 
ACTUAL FURNACE WORK. 



mi 

llii 
ill 
Si 


E 
a: 

1 

1 

1 
1 


1 

1 
1 

s 

390 
308 

899 


1 

'a 

•s 

< 

1 
1 


1 

s 
t 

i 

i 



1 
1 

3 

s 

< 

1 


s . 1 
s s 

■ 3 

1 L 

1 ss 

IF 


1 

i 

ll 


i 
f 

s 
■5 


1 

1 

1 

1 


1 
J; 


•s 

1 
1 


Sq. U. 
1685 


S-io-18 


Inside: 

-9CM 


1-63 


Sq.ft.. 


Sq.in 
Cufft. 

1-66 


SqJ^n. 
Sq.ft. 


Sq.ft 
Sqit 


SqJl, 
CuJt 

1-633 


Sq^ft. 
Sq!(.. 


• 


... 


J-lo-78 
4-S-50 


508 


Iniide Ouliide 


i-« 


,-,., 


1-30 


i-il 


,-,. 


... 


.... 


• 


4SO 
6so 


Outside: 


1-30 


... 


., 


l-ll ,1-13 
1 


1-J40 


,-,. 


(40 
110 


• 


631 


'ti 


'i 


16X36 


,-,. 


1-1.06 


-« 


.-..,-„ 




,., 


• 


136s 


J" '05 


",?." ,„.. 


1-68 


.-..4 


! 


,-, 




461 
iot8 


s-e-so 

1-10-78 


'" 


Inside : 


,-...;,-.«-.„;,-,.,. '".igi^"™ 


160 


1 



350 HEATING AND VENTILATING. 

Furnace capacities to be increased by one-quarter for bitu- 
minous coals from western Kentucky or from west of the 
Ohio river and by one-third for lignites and bituminous coals 
from the Rocky Mountain Region. 

167. Rules for Furnace Heating. — From the formulas 
given the following rules can be deduced, it being understood 
that the equivalent glass surface is equal to the area of win- 
dows and doors plus one-fourth that of the exposed wall expressed 
in square feet: 

First, To find area of grate in square inches: Divide 
equivalent glass surface in square feet by 1,25 or multiply by 0.8. 

Second. To find area of flue for any room in square inches: 
Divide equivalent glass surface in square feet by 1.2 for first flooTy 
by 1.3 for second floor, by 1.8 for third floor. 

Third, Make area of vent-flues 0.8 of hot-air flues. 

Fourth. Make area of cold-air box 0.8 of given areas of 
hot-air flues. 

Fifth. Take area of chimney smoke flue in square inches 
as one-twelfth that of the grate, with one inch added to each 
dimension. 

168. Abstract for Furnace Specifications. — The following 
suggestions are given for the purpose of calling attention to 
points of construction, which should be fully considered in the 
complete specifications furnished a contractor. 

The location of furnace, hot- and cold-air pipes, vent-pipes, 
smoke-pii)e, and registers should be shown on accompany- 
ing drawings. 

The furnace should be gas tight and built of cast iron (or 
steel) in such manner as to be free from expansion strains 
and from danger of warping or cracking in use. Grate should 
be of shaking pattern, containing 50 per cent air-space and 
adapted to burn the coal needed. The heating surface should 
be of form best adapted to transmit heat to the surrounding 
air. Furnace should be provided with all necessarj* fire and 
clean-out doors, vapor-pan, and a complete set of fire-tools. 
Complete drawings and specifications should be submitted. Draft 
for fire-doors should be arranged to be operated from above. 



HEATING WITH HOT AIR. 351 

The furnace may be either brick-set or portable-set as desired. 
If brick-set, the wall should be well laid, of good, hard mer- 
chantable brick, in such manner as to leave an air-space between 
the inner and outer walls. If portable-set, the casing out- 
side the air-chamber should be made of two thicknesses of 
No. 24 galvanized iron, ^ inch apart, and with the space between 
filled with asbestos. The casing should in all events be pro- 
vided with doors for cleaning out dust from the air-pipes and the 
air-chamber, also with collars for the hot-air pipes. 

The smoke-pipe should be of size noted in sp)ecifications, 
and should be provided with check-draft for admitting air 
into the flue, which can be op)erated from the rooms above if 
desired. 

The hot-air pipe should be made of DC bright tin-plate, 
and should be covered with two thicknesses of asbestos paper 
to reduce radiation. The hot-air pipes in the partitions should 
be made double, with ^-inch air-space. In case this cannot 
be done the pipe should be covered with asbestos paper. All 
hot-air pipes should be at least one inch from woodwork, and 
if the pipes are not double the woodwork should be pro- 
tected by a covering of asbestos paper firmly secured in place. 
Hot-air pipes passing through wooden partitions should be 
guarded by a double-collar of metal giving at least 2 inches of 
air-space. Disk dampers should be located in all hot-air pipes 
excepting one. 

The cold-air box should be made of masonry Or of matched 
wood lined with tin or zinc, and provided with regulating- 
damper, and with a screen for removing dust; also with doors 
for cleaning. 

Hot-air pipes for wall-registers should have rounded end 
above register-box. 

Registers to be of sizes shown on plans and finished as 
required. The register-boxes to be of shape shown in draw- 
ings and to be finished in the best manner. 

Automatic draft-regulators of good quality, operated by 
change of temperature, are always desirable. 



CHAPTER XIV. 



MECHANICAL VENTILATORS. 



169. General Conditions. — Attention has been called to the 
fact that air will not flow unless a difference of head tends to 
ui^e the particles from a higher to a lower region of pressure. 
This difference of head may be produced, as already shown, 
by heat or by mechanical action, and in every case produces 
a velocity which, if friction and other r esista nces be neglected, 
may be expressed by the formula v = Vigh. in which A is the 
difference of head in feet of air 
and is equivalent to the difference 
of pressure. If the resultant 
pressure is less than that of the 
surrounding atmosphere, a partial 
vacuum is formed and the flow 
is said to be caused by suction; 
if, on the other hand, the pressure 
is greater, a plenum is formed 
and the flow is said to be due to 
pressure. In the case of a heated 
chimney or flue the pressure is 
less than atmospheric and the 
flow of air Is caused principaUy 
by suction, as would also be the 
case with an exhaust-fan; with a blowing-fan, however, the flow 
would be principally caused by increase of pressure. 

The principal machines used for moving air for ventilating 
purposes, either by pressure or suction, are the centrifugal 
fans or blowers, the positive- volume blowers of the piston or 




Fio. 233,- 



MECHANICAL VENTILATORS. 363 

rotary type, and the jet-pumps from which are discharged 
jets of steam or compressed air. The requirements for good 
ventilation demand that large volumes of air must be moved 
at a comparatively low velocity and pressure, which is not 
a favorable condition for high efficiency, and can in general 
be better satisfied by the centrifugal fan or blower than by 
any other machine; it may also be stated that the fan is com- 
paratively cheap to install, is simple in construction, and possesses 
a fair efficiency. 

170. Steel Plate Fans or Blowers consist of a wheel provided 
with several blades or vanes approximately radial and either 
plain or curved; this wheel is set in a casing or housing arranged 
to prevent the return of the air from the delivery side to the 
suction side and direct it to the point desired, and is con- 
structed so that it may be rotated by some external motive 
force. A fan used for ventilating buildings is shown on the 
preceding page, as it appears when removed from its casing. 
In this particular type of wheel the blades are radial and 
plane nearest the center, but are curved backward and narrowed 
at the outer circumference. The proportions of the wheel 
are varied to suit different conditions, but do not usually differ 
materially from those which Mr. W. Buckle* found to give 
the best results and which are given in the following table. 
In addition are given the proportions in ordinary use in parts 
of the diameter of the wheel, D, 

Buckle's Proportions in 

Proportions. Common Practice. 

Diameter of fan-wheel D D 

Diameter of inlet (single) o. $/> 0.6 to o. 7/? 

Diameter of inlet (double) 0.4 to o. 5/) 

Width of wheel at outer circumference. . . o. 2$D o . t^D 

Width of wheel at inlet circumference ... o.^D o . 5 to o. 5/) 

Length of blade radially o. 25Z) o. 2 to 0.3Z) 

The air enters the fan-wheel through the opening in the 
casing adjacent to and surrounding the axis; it is then thrown 
outward and compressed by the centrifugal force produced by 
the rapidly revolving blades; this causes a difference of pres- 

* Proceedings of Institute of Mechanical Engineers in 1847. 



354 



HEATING AHD VENTILATING. 



sure between the centre and circumference of the wheel, which 
in turn produces a continuous flow of air from the centre out- 
ward. If the chamber leading to the inlet is restricted and 
the delivery opening unrestricted, the pressure at the centre 
may be less than that of the atmosphere, in which case the 
fan is said to act by suction or as an exhaust fan; if the outlet 
passage in the casing is restricted, more or less pressure will 
be produced, in which case the fan will be considered to act 
as a pressure fan. It should be noted that the blades or vanes 
in the wheels of the centrifugal blowers vary greatly in shape 
as made for different purposes and by different designers, and 




Fic. IJ4. — Ca^Dg for VeDtnating-fm. 



that, although the centrifugal fan has been used practically for 
more than two centuries, engineers have not as yet agreed as 
to the best proportions and best forms of the working parts. 
A number of examples of different design will be shown later 
in the chapter. 

The casing or framework surrounding the fan-wheel should 
be constructed so as to first permit or direct the flow of air 
to the centre of the fan-wheel, and second to receive the dis- 
charge of the fan and direct it as desired; from which It is 
evident that the form of the casing may be varied greatly 
to suit different conditions. The forms of casing usual in cen- 
trifugal ventilators for buildings arc those with plain sides, 



MECHANICAL VENTILATORS. 356 

having a periphery or scroll which is spiral in form and which 
contains considerable room or clearance in excess of that required 
for the fan- wheel. The clearance. space in the casing is essential 
for noiseless operation and efficient results, as will appear later. 
The following clearances or distances between wheel and casing, 
expressed in proportional parts of the diameter of the fan- 
wheel, Z?, are common in the best practice of fan construction: 

Least radial distance from wheel to casing. . . . .0.08Z? to o. 16D. 
Maximum radial distance from wheel to casing, o . $oD to i . ooZ>. 

Least side distance from wheel to casing o . 05Z? to o . o8Z>. 

• 

The inUl opening, G, Fig. 234, to the fan-casing is usually 
circular in form, concentric with the axis of the fan-wheel, 
located in either or both sides of the casing as circumstances 
may permit, and with dimensions as given in a preceding table. 

The outlet or discharge opening in the fan-casing often 
extends for exhaust-fans completely around the periphery, but 
in case of pressure-fans delivering into conduits or pipes the 
periphery is closed except at the opening for discharge, which 
should be constructed so as to permit delivery with the 
least possible shock. As will be shown later, the exhaust-fan 
is more efficient when discharging into an expanding conduit 
or chimney of proper shape than when delivering freely into 
the air. 

The ordinary forms of casing differ from each other prin- 
cipally in the position of the discharge opening, as shown in 
Figs. 23s to 237; thus in Fig. 235 the discharge is horizontal 
and at the bottom, in Fig. 236 it is horizontal and at the top, 
and in Fig. 237 it is vertical and at the top. The casings are 
made with discharge at any angle or position desired, and 
single or double as required. There is usually only one inlet 
provided for fans to be used as exhausters and it is generally 
located in the side of the casing opposite the motor or driving- 
wheel and is always concentric with the axis of the wheel. 

The centrifugal fans described above and shown in Figs. 233 
to 237 have a small number of nearly radial vanes around the 



356 



HEATING AND VENTILATING. 



shaft and from the material generally used in their construction 
are usually called Steel Plate fans. They operate almost equally 
well as blowers or exhausters and are very extensively used in 
the ventilation of buildings. 

These fans are a standard article upon the market, being 
sold by several manufacturers in sizes ranging from 30 to 350 
inches. The size usually designates the approximate height 
of the casing in inches. The large sizes are more efficient than 
the small ones, but the height of basements, etc.. do not as a 
rule permit them to be used for ventilating buildings. 

A form of setting known as " three-quarter housed, 
which the lower part of the casing is constructed of masoi 



I 







Fig. *3S. — Bollom Hori- 
zon lal Distharge. 



or concrete and the lower part of the wheel placed below tlie 
floor line, is used for large fans. (See Fig. 237.) 

The centrifugal fan may be driven by any convenient type 
of motor, and several types are suggested in the various figures 
referred to; in Figs. 235 and 237 are shown fans driven by 
direct connection to a steam-engine; while In Fig. 236 is shown 
a fan driven by direct connection to an electric motor. 

171, The Guibal Chimney or discharge- tube, invented about 
fifty years ago by M. Guibal, is extensively used in connection 
with fans for mine ventilation, and would doubtless prove 
equally beneficial for ventilating work; it is in effect a continua- 
tion of the casing at the point of deliverj", so as to form a trumpet* 
shaped or expanding tube through which the air is dischai 




MECHANICAL VENTILATORS. 



357 



without shock and with a gradual reduction of velocity. It 
has been found that an expanding discharge-tube with gradual 
curves m the general form of the vena contracta adds greatly 
to the efficiency, for the reason that the reaction due to shock 
at delivery is largely overcome, and the full momentum is 
utilized in moving the air. 

The Guibal fan is constructed in such a variety of forms by 
different designers that no special description is possible, the 




Fio i3» —The Cuibal Fan and 
Chimney 



only essential characteristic bemg the expanding chimney. One 
form of this fan is here shown. 

172. Multivane Fans. — To meet the demand for a fan to 
occupy less space than the Steel Plate fan, a tj-pe, known as the 
Multivane, having a large number of vanes usually curved 
forward and operated at a high rotary speed, was designed. A 
fan designed by Professor Ser of Paris is a good example of an 
early form of this type. The impeller of this fan consists of 
a circular plate fixed on a shaft and carrying on each side thirty- 
two curved vanes, each of which is a portion of a cylindrical 



858 HEATING AND VENTILATING. 

surface whose generatrices are parallel to the shaft and whose 
transverse section is circular; the width of the vanes is con- 
stant, and they are so arranged that inflow takes place without 
shock and that the air is discharged from the fan in the direc- 
tion of 45° with the tangent to the outer periphery. The 
air enters the fan on both sides, and after passing through it 
enters a volute which conducts it to an expanding chimney, 
from which it escapes into the atmosphere. The volute is so 
designed that there is as Utile loss of energy as possible at entry 
from the fan and while passing through it; the sides of the 




Fig. 340. — Section Through Ser Ventilator. Fig. 141. — Impeller o( Sirocco Ftm. 

chimney are inclined at not more than i to 8 in order to avoid 
the loss due to the sudden enlargement of passage. 

The " Sirocco " fan which was designed by Mr. Davidson 
in Ireland is a well known example of the Multivane type. 
This fan is shown in Figs. 241 and 242 and is also constructed 
with two inlets. The characteristics in its design are: 64 vanes 
having a depth radially of ^ diameter of impeller and a length 
equal to one-half the diameter of the impeller. 

The vanes are cur\'ed forward to meet a tangent to the 
periphery at an angle of 32.5° and an angle of about 62° with a 
tangent to inside circle. 

These fans are constructed In sizes from i to 12, correspond- 
ing to heights of casing of loj to iz6j inches and diameters of 
impeller of 6 to 72 inches. The manufacturers claim capacities 



MECHANICAL VENTILATORS. 



359 



K>f 280 to 38,400 cubic feet of air per minute against one inch of 
f water column at 1080 to 175 R.P.M, 

In addition to the fans shown numerous forms have been 
^designed which have not proved to be of great practical impor- 
f'tance and which, for want of space, cannot be considered more 
in detail. 

A form of centrifugal fan or blower, shown mounted in a 
^^ brick casing in Fig. 243, is often used where the conditions are 
^Kpot favorable for the form shown in Fig, 233. It is known as 
^Bthe cone blower, for the reason that a cone-shaped guide is used 




1 durect the entering air from the center toward the drcum- 

erence. In construction it consists of a plate mounted on a 

ihaft to which are connected the cone guides and the various 

tvanes required to give the centrifugal motion to the air; its 

inciple of operation is identically the same as that of other 

s of centrifugal blowers. 

173, Propeller or Disk Fans. — The name is applied to a 

5 of fans which move the air forward by impact as well as 

ntrifugal force. In general these fans are mounted in a 

E^lindrical casing and have a number of vanes or blades which 

: arranged with a diminishing pitch from the centre to the 

aference somewhat similar to the blades of a propeller. 



HEATING AND VENTILATING. 




MECHANICAL VENTILATORS. 361 

Three forms are shown, one with plane blades, Fig. 246, one 
with curved blades driven by a motor. Fig. 247, and one with 
helix-shaped or screw blades, Fig. 248, into which the air is 
guided by fixed vanes. 

The fans in this class are useful for moving large volumes 
of air with comparatively low pressures and velocities. They 
are as a rule not adapted for use where there is any great resist, 
ance to be overcome. 

174. Volume or Positive Blowers. — This name is appli- 
cable to that class of blowers which deliver a fixed volume of 
air at each revolution and which are positive in their action 




"D T 

Fig. 249. — Section of the Root Positive Blower. 

and prevent the return of compressed air, not by uniform action 
of centrifugal force, but by use of valves or by contact of the 
rotating parts. A great variety of blowers have been constructed 
that could be put in the above classification, but the only ones 
at present in extensive use are piston blowers and two forms 
of rotary blowers shown in Figs. 249 and 250. Blowers in 
this class are well adapted to move small volumes of air at high 
pressures and are extensively used for blast-furnaces and similar 
work. They are not well adapted for ventilators or for any 
other purposes requiring large quantities of air at comparatively 
low pressures. 

175. The Theoretical Work of Moving Air. — The work 
performed by the fan is made up of the resistance due to moving 



362 HEATING AND VENTILATING. 

and compressing a detinite amount of air, and can always 
be considered as equivalent to moving a given weight of ail 
through a height or head which is equivalent to the sum of the 
velocity and pressure heads expressed in feet of air at the 
density corresponding to the air after being compressed. 




Fic. i$o. — Section of the Connessville Positive Blower. 

For the low pressure required for the ventilation of building: 
the work of compression is only a small part of one per cent, 
the total work and is neglected in the following formulas: 

Let Q=volume of air in cubic feet per minute, 
d = weight of air, in lbs. per cubic foot, 
d' = weight of water, in lbs. per cubic foot, 
h — pressure head in feet of air against which air ismoi 
ft'=pres5ure head in inches of water against which air 
is moved. 
Work = force X distance = weight X height =QdXh. 

work in Jt.-lbs. per minute QdXh ^ X2 d \ 
33,000 ~33.ooo~ 33.000 

d' may usually be taken as 62.4 without appreciable 1 
which gives 






L^ 




= 0.0001 S75()A'. 



HEATING AND VENTILATING. 



This equation shows that the work done in moving air is 
independent of the density, but this is not exactly true in 




:xMN\^ii I 






practice as the speed of the fan must be increased as the density 
of the air decreases, and a little more is lost in friction. 




MECHANICAL VENTILATORS. 365 

176. Work of Moving Air through Pipes. — To the work 
needed for moving the required volume of air at the desired 
velocity must be added that which is necessary to overcome the 
resistance in the fan and in the various pipes or flues. As 
previously explained, the loss of head due to friction in a circular 
pipe can be expressed by the formula 

/ i^ 
d 2g 

in which A = loss of head in feet of air, J = diameter in feet, 
/ = length in feet, i> = velocity in feet per second. 

Let /> = loss of head expressed in ounces per square inch; 
d' = diameter in inches; 2^ = 64.32; 4^=0.025. We have 

// = ii5/>at 50° F.; 

(2573X115)- 

which is the formula representing the loss of pressure in a pipe 
of galvanized iron carefully made and erected, with all internal 
laps extending in the direction of the air movement, assumed 
in the work on " Mechanical Draft," published by the B. F. 
Sturtevant Co., Boston. 

The work done in overcoming friction, expressed in foot- 
pounds per second, is equivalent to the resistance, expressed 
in pounds, multiplied by the space passed through in one second 

of time. If F denote the area of cross-section, p the resistance 

Fp 
per square inch in ounces, then -7- will equal the total resistance 

in pounds; if v denote the velocity in feet per second, it will 

equal space passed through in one second. Hence the work 

Fpv 
done in one second will equal — 7"; this result divided by 550 

will equal the horse-power, P: 

88cx)" 



366 HEATING AND VENTILATING. 

From these two formulas can be calculated the drop or loss in 
pressure in ounces in a given pipe-line, and also the horse- 
power required to overcome the resistance of moving air at the 
given velocity through the given pipe. 

Table No. XXIII in the Appendix gives such values for 
the principal pipe sizes and for a length of pipe equal to lOO 
feet. For any other length multiply the results in the table 
by iV ^^^ square root of the given length in feet, for the reason 
that the work required varies as the square root of the length. 

177. Dimensions of Pipe-lines for Air. — Formulas for comput- 
ing the flow of air through a pipe under various conditions 
have been fully discussed. For practical use Table No. XXV 
in Appendix has been computed, which gives the diameter of 
circular pipe, also the corresponding side of a square pipe, for a 
given discharge in cubic feet per minute and a given length, 
with a drop in pressure equal to an inch of water-column (0.58 
ounces per square inch) and a temperature of 100° F. The 
relation of the discharge to the diameter of a circular pipe is also 
shown in the diagram Fig. 251, in which the ordinates give 
the diameter of pipe corresponding to a given discharge repre- 
sented as abscissa, the varying lengths of pipe-lines being 
distinguished by different lines. The scale on the left corre- 
sponds to the lines inclined upward to the right and to the 
upper scale at the bottom, that on the right to the lines inclined 
upward to the left and to the lower scale at the bottom. To 
use the diagram, suppose it be required to find the diameter 
of a circular pipe whose length is 500 feet and whose capacity 
must be 20,000 cubic feet of air per minute; find intersection 
of vertical line from 20,000 with upper line marked 500, thence 
horizontally to the scale at the left, which is intersected at a 
point corresponding to the required diameter, which by inter- 
polation is found to be 38.5 inches. If the capacity is to be 
90,000 cubic feet per minute and length 100 feet, find the 
intersection of vertical from 90,000 with lower line marked 
100, and read diameter on right, which will be found to be 52 
inches. 

The flow of air through other than circular pipes has not 



MECHANICAL VENTILATORS. 367 

been discussed in this work; it is known, however, that for 
any pipe the resistance to the flow varies as the mean hydraulic 
radius, a quantity equal in every case to the area of cross-section 
divided by the perimeter which is subjected to friction; for a 
circular pipe this becomes one-fourth part of the diameter, for 
other cases it must be computed. 

From this relation we have constructed a diagram or chart, 
Fig. 252, which enables a designer to select a rectangular pipe 
having dimensions which give a carrying capacity equal to a 
known, circular pipe, it being supposed that one of the required 
dimensions of the rectangular pipe is known. 

In the diagram Fig. 252 the diameter of the known circular 
pipe is given as ordinate, corresponding to the scale at the 
left; one of the dimensions of the equivalent rectangular pipe 
is given as abscissa, the other is denoted by a series of lines 
corresponding to the scale at the right. Thus to find a 
rectangular pipe with the same carrying capacity as a 30-inch 
circular pipe, one dimension of which shall be 40 inches, we 
find the intersection of the horizontal line from 30 on the scale 
at the left with the line marked 40 on the scale at the right; the 
result read on the bottom scale is 19, which indicates that a 
rectangular pipe with dimensions of 19X40 inches is equiva- 
lent in capacity to a circular pipe with a diameter of 30 inches. 

The results of a series of tests carried out at the Government 
Testing Plant at Washington under the supervision of Naval 
Constructor D. W. Taylor to determine the head lost in friction 
of air moving through pipes gave the following results: 

Coefficient of friction, /, constant for different sizes and 
velocities and having values for galvanized iron pipe from 
0.00008 to o.oooi depending upon the alignment and surface 
of duct, which are to be substituted in the following standard 
formula: 

Hf=4f -.v^ for square and round pipes, 

Hf=4 / r^i^ for rectangular pipes having sides h and nh. 



368 HEATING AND \T:XTILATING. 

i6i. Focmulas for tiie Approximate Dmensiaos and Cmpmdr 
ties ci Fans. — There are {ormiilas in more or kss general use 
which give the relations of capacity to proportions with sufficient 
accurac}' for ordinary use. 

Z>= outside diameter of impeller, in feet, 
ir = width of impeller at peripher}-, in feet, 
Di = diameter of inlet, feet, 
Q = capacity, cubic feet of air per minute, 

// = eflective head in feet of air. 
//'= effective head in inches of water, 
r = velocity of air corresponding to A, 
F'= peripheral velocity in feet per minute, 

f = peripheral velocity in feet per second, 
A = blast area in square feet. 

In any centrifugal fan the effective static pressure produced when 
the outlet is closed should be equal to r^'-r-2^, which is the pres- 
sure due to the centrifugal force. This would be exactly true in 
e\xTy case regardless of the shape of vanes if there were no leaks 
and the air had a uniform angular velocity of rotation entirely 
to centre of impeller. If the outlet be slowly opened while fan 
is running, the pressure due to centrifugal force, as given above, 
will be partially utihzed in overcoming friction in fan and in 
giving the radial component of the velocity of the air passing 
through impeller, but at the same time a new source of pressure 
comes into existence, since the head corresponding to the velocity 
at which the j)articles are discharged from impeller may be 
converted into pressure. For radial vanes, the maximum value 
for the pressure due to the tangential component of the velocity 
of the particles leaving vanes is also equal to v^-7-2g. The sum 
of the maximum values of these two pressures is v^-i-gy which 
is often termed the theoretical head, but it is apparent 
that this value is not obtainable from any radial vane fan 
because the two conditions necessary cannot exist at the same 
time. 



MECHANICAL VENTILATORS. 369 

For fans of the steel plate type having vanes approximately 
radial, the effective pressure may be safely taken as 

A=-, (i) 

which for air weighing 0.075 ^^d water 62.4 lbs. per cubic foot 
gives 

» = 4003VA' (nearly), (2) 

7rDiV = 400oVA', 

' A' = 7 ^2= 0.00000006 1 6Z)2xV2 (2) 

A well known fan of the multivane type having vanes curved 
forward, making an angle of 22^° with the tangent at periphery, 
gives 48% greater pressure for the same peripheral speed or may 
be operated 17.5% slower to give the same pressure as a radial 
vane fan. 

The efficiency of the steel plate fan decreases as the diameter 
of the inlet increases, and it has been found that fans having 
inlets proportioned according to the following formula give good 
results, 




(4) 



For steel plate fans make ^=0.93 for single inlet, 

« = o.74 for double inlet. 

The blast area is the ratio of the capacity to the velocity in 
feet per minute corresponding to the effective pressure, and is a 
term of the same general nature as the equivalent orifice used 
by Murgue. 

Blast area A = y. 



370 



HEATING AND VENTILATING. 



This ratio bears a definite relation to the dimension of a fan 
which is constant for all fans of the same relative proportions 



QDW 
V~ 



tn 



For steel plate fans, »»=3, and for V = V' =tDN. 



(s) 



. (6) 



For the multivane fan mentioned above, 



which gives 



f» = i.87 and 7 = 1.2157' = i.2i5TZ)iV, 



g= ^g =2.047rZ>2iVH^ 



Experiments show that well constructed fans of the steel 
plate t>'pe having inlet proportioned as in (4) will have 
efficiencies bearing approximately the following relation to the 

ratio -jr as shown by experiments. 



~D 


Efficiency. 
Per cent. 


0.40 
0.50 
0.60 
0.70 
0.80 


62 

57 
51 
44 
36 



The power required to operate a fan may be determined by 
dividing the power required to move air as computed from a 
formula given in Art. 171 by the efficiency of fan, which for 
steel plate fans may be taken as 45% ^or the average size of 
fan used in the ventilation of buildings. 



v=eM 



(6) 



MECHANICAL VENTILATORS. 

































































^ 




' 
























\^ 


— 


— 


1 


/ 








- 














\ 








/ 








/^ 




■~ 


> 




II.- 










=1 ■ 






■ — 


L^ 




1 — 


— 


~/ 




•> 


< 




















/ 








/ 




/ 








■^ 


_ 












1 








/ 




/ 
























1 






/ 




/ 






























y 




/ 




























-i^ 






/ 






























as 


h 




/ 
































•i 


3> 




■/ 













































































Blast Ana. 
Fig. 153.— Teat of Sirocco Fan No. *i.— (Square outlet io"Xio".) 

















































^ 


" 












\ 
























¥ 






























5^ 

via"! «■ 

liii 






1 






















V 






































rN 






































■ 


" 




■ ^ 
















y 












-- 








/ 












^ 
























/ 










y 


















^ 


.^ 






ii 


S5 


/ 






^ 


<- 


^ 




















' 






==, 


y 


4 


^ 







































































Fic. IS4' — "^sst of Sturdevant Multivane Fan.— (Circular outlet ill" diameter.) 



178. Characteristic Curves of Multivane Fans.— The 
characteristic curves for the Sirocco Fan No. 2 J and the 
Sturdevant multivane fan were obtained from tests made at 



372 HEATING AND VENTILATING. 

Sibley College under the author's direction by Prof. W. M. 
Sawdon and Mr. T. B. Hyde. The results are here plotted 
against the equivalent orifice or the blast area, which is the 
volume of air deh'vered divided by the velocity corresponding 
to the total or the impact head. By using this method the 
characteristic cur\-es of the blower are put on an equal basis 
for comparison with other blower tests, under different condi- 
tions as to blower sizes and piping conditions. 

The scales used in plotting these curves are multiplied by 
looo to get the ^-olume of air and by lo to get the efficiency- 



^-~^/ 


:, -.r 7"-- 


M^^ilJ ^^ 


:z^L/i:;:::^ 


,^l 7 T, 


7t J 


i :t 


|:j_:::::::"^ 


./ 2 _ 


li 


/ :::: 



REDUCED ORIFICES. 
Fig. ?ss. — Characterislir Curves of Rateau Faiu. 



in per cent. For instance with the Sirocco fan, taking a blast 
area of 0.5, then Curve I reads directly as 4J inches of water 
impact head, and Curve II reads 4.25X1000 or 4250 cubic 
feet of air per minute, and Curve III reads 5X10 or 50*^ 
efTicicncy of the fan, while Cur\c IV reads directly as 5.85 
horse-powcT input lo drive the fan. 

Professor Rateau has modified the Murgue theory by 
substituting (}, \ gli (or the value of the equivalent orifice 
Q/.Os^ 2gli. ihi:^ being done in order lo simplify the inter- 
mediate computalions, the results c.xtcpt for the value of the 
coeflicients being otherwise the same. Rateau also used a 



MECHANICAL VENTILATORS. 



373 



" reduced orifice " (b) as equal to the equivalent orifice divided 
by the square of the external radius, r, of the fan inlet; that 

Q 

is, b = — y^. He uses the term " manometric power," M, 

rVgh 
as equal to gh/u^, in which u is the peripheral velocity of the 
fan. In accordance with Rateau's notation a fan may be 
represented by an equation of the following form, where s, t, and 
u are constants depending upon the construction 



I ^^ . o . 



In a series of tests made by Mr. Brian Donkin the following 
values of these constants were found: 



Number 
of Fan. 


Value of Constants. 


s 


t 


u 


VIII 
VI 
X 
XI 


0.136 
0.192 

2.43 
10.05 


14.18 
5.8s 

13 ss 

126.4 


1.690 
1.666 

I -755 
3SI 



The characteristic curve of the Rateau fan. Fig. 248, is 
shown in Fig. 255, which gives the manometric power and various 
eflSciencies for a series of reduced orifices. 

179. Maximum Pressure Produced by a Fan or Blower. — 
This quantity corresponds to the initial depression in Murgue's 
theory and is obtained only at the time when the work imparted 
to the fan is all utilized in overcoming resistances, as, for instance, 
in a pressure fan when the discharge opening is entirely closed. 
For this case, if there is no loss of energy due to eddies or other 
resistances, we shall find, since the work done is equal to the 
weight moved or the pressure H overcome in one second 
multiplied by the space, that 



.u 



2 



Hihu) = W-, 



374 



HEATING AND VENTILATINO. 



from which 



B = 



But W=cFu, hence 



W-. 
g 



H=cF 



gi 



and we have for unity of volume and area, since Q and F 
each = I, 

^=7 (" 

From the last equation it is noted that the "^^Timum pres- 
sure produced may be equal to twice that due to the head 
producing the same velocity which is the same result as obtained 
by Murgue. 



MAXIMUM PRESSURE DUE TO SPEED OF FAN. 



Speed of 
Periphery 

of Pan. 
Pt. per Sec. 


Difference 

of Pressure. 

Inches of 

Water. 


Speed of 
Periphery 

of Pan. 
Pt. per Sec. 


Difference 

of Pressure. 

Inches of 

Water. 


Speed of 
Periphery 

of Pan. 
Pt. per Sec. 


Difference 

of Preaaore, 

Inches of 

Water. 


49.21 


1.08 


77.10 


2.66 


98 75 


436 


50.19 


I 13 


78.41 


2-75 


1 100.08 


4.48 


52.82 


1.25 


80.05 


2.87 


101.71 


4.63 


55 12 


I 36 


82.02 


3 00 


103.02 


4 75 


58.07 


I 51 


83 01 


308 


■ 104.33 


4.87 


60 04 


1. 61 


85.30 


3 26 


105 30 


5 05 


62 67 


1.76 


86.62 


3 36 


107.28 


5 IS 


64 . 96 


I 89 


88.58 


3 51 


108.27 


S.24 


66.93 


2.00 


90.55 


3^ 


109 58 


S.37 


70.21 


2. 20 


91.86 


3 77 


no 80 


s 50 


12 50 


2 35 


Q4.4Q 


3 99 


112 53 


563 


74 80 


2.50 


96.13 


4 13 


113 85 


5. 76 


75 70 


2 57 


97. 77 


4.27 


114 50 


587 



In general the increase in pressure produced will always 
be less than the theoretical, if we denote the coefficient indi- 
cating this ratio by A'. Then for the case when velocity of 
discharge is zero, we have 



J? 



(8) 



MECHANICAL VENTILATORS. 375 

,The actual increase of pressure produced will be lessened 
by increasing the velocity of discharge, as indicated by the 
formula, 

For dimensions of outlet, F, less than or equal to those of 
the inlet, f 0, we have as nearly true 



''=''4^-fJ- 



Substituting this value in the preceding equation, we have for 
the resultant pressure-head in feet of air 



h = 

g 



i'-B' 



For the pressure expressed in any other units the results 
must be divided by the ratio of the weight of the unit desired 
to that of one foot of air. Call this ratio 6; then we will have 
for maximum pressure in the desired unit 

H^-— (10) 

The table on page 376 gives values of relative density d 
expressed in feet and inches of water, the barometer being 
29.92 inches. The value of the coefficient K will depend upon 
the construction of the fan, the casing, and chimney; but, as 
shown by Murgue, its value for an imcovered exhaust fan can- 
not exceed 50 per cent. Its value varies greatly with different 
fans and with the area of discharge opening; it was found by 
experiments by Buckle to have an average value, for ventilat- 
ing-fans, of 0.617, in which case the equation (8) becomes 

^=o.6i7y (80 



376 



HEATING AND VENTILATING. 



RELATUE ^lEIGHT OF WATER AND AIR. 





peratnre. 


Weight per 


Cubic Foot. 




Tetn 














Water-coinmo of 


D««rce«. 

Fahrenheit. 




Centigrade. 


Water. 


Air. 


I Foot. 


I Ixtcfa. 


32 







62.42 


0S64 


722.4 


60.2 


41 


1 
1 


5 


62.42 


07Q3 


7S93 


65.8 


50 




10 


62.41 


0771 


S01.2 


66.7 


5Q 




15 


62 38 


. 0765 


S15 5 


67.9 


68 


■ 


20 


(>^ S5 


0752 


S:S 8 


69.1 


S i 




25 


62 26 


0740 


841 3 


70.1 


86 




30 


02 17 , 


0728 


S54 


71 2 


95 




35 


62 08 


0717 


S6q S 


72.2 


104 




40 


oi 07 


0704 


88^ 2 


73 3 


113 


■ 


45 


61 85 


0.0693 


8Q4 2 


74 5 


122 




50 


61 70 


0682 


904 7 


75 4 


131 




^ «» 

:>:> 


61 54 


0.0672 


975 8 


81 3 



Considering the weight of one cubic foot of air as .08 pound, 
the following equations will show the relation of the velocity 
of the tips of the blades to the pressure in Buckle's formula: 



When p 
When p\ 
When //i 
When //2 



pounds per square inch, u 
ounces per square inch, u 
inches of mercury, u 

inches of water, w 



3iov7>. 
8o\ 7>i. 

220\ hi 
60 \ 7/2. 



The table on page 378 shows the relation of the peripheral 
velocity of the fan to the pressure produced, computed from 
the formulas as given above. The table will be found to give 
lower pressures than the maximum actually produced with 
most fans when the outlet is closed, hence it can be considered 
a safe one to use. It is to be noted that this table gives the 
pressures only when the fan is operating to deliver a small 
volume of air. To determine the pressure when the outlet 
has an area F, and the inlet an area Fi, multiply the tabular 



/ ^\2 

results by 1.62(1—^- I . 



MECHANICAL VENTILATOBS. 



377 



The effect of varying the area of discharge outlet is shown 
in the diagram Fig. 256, which shows the pressure in inches 
of water produced by a speed of 500 revolutions per minute in 
three different fans, each having a fan-wheel 4 feet in diameter 
and an inlet 22 inches in diameter. In one case the blades 
were radial, in another case bent forward, and in a third case 
bent backward. It will be noted that the highest readings 
obtained when the outlet was closed agreed very closely with 

































i 


























~ 












































pm 










r" 














































,E 


























































n 


HT 




w 


ra 


• 




k 




IIR 


FTC 






\\ 


















































































































































































*.. 






"1^ 






















































,J.[ 






^ 


j,\ 




























































s 


N 


















































;-•" 










s 
















































i- 










% 
















































r 


' 












\ 


> 


























































^ 






























































^^ 


^ 


^ 




















































































































































































































■ 






































5' 




h 


















































































. 












1 


J) 








t 









Ji 




J> 








» 




Ji 


* 


» u 



Fig. ;s6. — Relation of Pressure to Area of Outlet. 



considerably greater than in Buckle's table given above. 

180. The Velocity and Volume. — The velocity of air in feet 
per second discharged from fan will be, in accordance with the 
notation used, 



and that entering 



v = eu = 2ireRn =vDen, 



= iv — eiu = zvRein = irDein. 



(>.) 



378 



HEATING AND VENTILATING. 



PRESSURE CORRESPONDING TO VARIOUS PERIPHERAL VELOCITIES 

OF FAN. (Buckle's Formula.) 

Allowance made for Increased Density of Air. 



Peripheral Velocity. 


Pressure Produced. 


Feet per Second. 


Feet per Minute. 


Ounces per Square 
Inch. 


Inches of W^ter. 


I 


60 


0.000156 


0.000269 


5 


300 


0.0039 


0.0068 


ID 


600 


0.0156 


0.0269 


IS 


900 


0.035 


0.061 


20 


1,200 


0.062 


0.107 


25 


1, 500 


0.098 


0.167 


30 


1,800 


0.140 


0.281 


40 


2,400 


0.250 


0.430 


so 


3,a» 


0.38 


0.65 


60 


3,600 


0.52 


0.89 


70 


4,200 


0.73 


1.26 


80 


4,800 


0.96 


1.65 


90 


5,400 


I. 21 


2.08 


100 


6,000 


I 49 


2 57 


no 


6,600 


1.78 


3 07 


120 


7,200 


2. II 


363 


130 


7,800 


2.46 


4 24 


140 


8400 


2.83 


4.87 


150 


9»ooo 


3 23 


5 57 


160 


9,600 


367 


6.32 


170 


10,200 


4.16 


7 14 


180 


10,800 


4.70 


8.09 


190 


IMOO 


5 29 


9 15 


200 


12,000 


5 93 


10.20 


210 


12,600 


6 59 


II 34 


220 


13,200 


7.27 


12.51 


230 


13.800 


7 97 


13 78 


240 


14,400 


8. 69 


14 97 


250 


15.000 


9.41 


16.19 


260 


15,600 


10.17 


17 49 


270 


16,200. 


10.9s 


18.84 


280 


17.000 


II 75 


20.25 


290 


17,600 


12.56 


21.61 


300 


18,000 


13 39 


23 04 



The cubic feet of air supplied per second will equal cir- 
cumferential inlet velocity multiplied by area of cross-section 
of fan inside of the vanes: 

Q = v'b'wd = iVJ'tJ = eiub'-Kd = eiirDb'Trdn 

^(T^eiHDdb')n (12) 



MECHANICAL VENTILATORS. 379 

i8i. Work Required to Run a Fan. — The work is equal to 
the square of the velocity as expressed in (ii) multiplied by 
the mass moved, which in turn is equal to the weight divided 
by twice the force of gravity {2g), That is. 



Useful work in foot- 
pounds per second 



r.j^^=«;.=^-'*'»' 



2g 2g 2g 



Substituting in above Q—eiub'vdy 



tJ^VA^^ (13) 

2g ^' 



Substituting in above u = tZM, we have 



ij^ 



r=-^6'(/Z?3^n3, (14) 

2g ' 



from which it would appear that the work to drive a fan will 
increase with the cube of the number of revolutions. 

182. Application of Theory. — The equations which have 
been given are general ones applying to all centrifugal fans 
regardless of form of blade or of entrance and admission 
passages. From equation (11) it is noted that the velocity of 
the discharge-air varies with the velocity of the tips of the 
blades. The value of the coefficient e depends on the pressure 
which opposes the delivery of the air, the velocity of the fan^ 
and probably also on the form of blades. For fans working 
against a pressure of about i ounce per square inch or about 
1.73 inches of water this coefficient seems from practical data 
to be about 0.32, increasing to 0.4 or 0.5 with free delivery. 

In the ordinary construction of ventilating-fans the width 
V and inlet diameter d are usually taken in a fixed proportion 
to the external diameter of the fan-wheel Z), as noted in the 
table of proportions, and so that the product of Vd will equal 
0.2 to 0.25/)^. 



380 HEATING AND VENTILATING. 

Substituting in equation (12) the following values for the 
coefficients: 

11^ = 9.94 = nearly 10; 

6=0.4, average velocity of discharge air to periphery velocity; 
i=o.6 coefficient of supply to inlet; 
J6'=o.2Z>2 — 

() = .48Z)3 (15) 

By actual experiment this coefficient is found to vary with 
change in resistance, as explained later, from 0.3 to 0.6. 

If we substitute the value of the above coefficients in equa- 
tion (14), and also the value of r=o.8, and divide by 550, 
we have, as a value of work performed reduced to horse-power, 

T =0.00001 2 (Z)*«^) ver>' nearly. . . . (16) 

The above results are for a fan working with a moderate 
resistance, and in practice the last coefficient wiU vary, being 
less as the resistance is greater; it is approximately correct when 
the deliver)' pressure is one ounce per square inch, and decreases 
for higher pressures and increases for lower pressures, being in 
both cases essentially as expressed in the following rules: 

183. Practical Rule for Capacity. — By referring to formula 
(12) it is noted that the capacity is equal to the product of the 
constants multiplied by width of wheel, diameter of inlet, and 
bv diameter of fan-wheel into the number of revolutions. 
Since, in accordance with common practice, the last three 
proportions are varied together, we shall have as a practical 
rule for determining the capacity of fans with proportions 
similar to above the following: 

Rule. — The capacity of fatis, expressed in cubic feet of air 
delivered per minute, is equal to the cube of the diameter of the 
fan-wheel in feet multiplied by the number of revolutions, muUi- 
plied by a coefficient having the folloiuing approximate value: 

For fan with single inlet delivering air without pressure, 
0.6; delivering air with pressure of i inch. 0.5; delivering air 
yi\Xh. pressure of i ounce, 0.4. For fans with double inlets the 



MECHANICAL VENTILATORS. 381 

coeffident should be increased about 50 per cent. For prac- 
tical purposes of ventilation the capacity of a fan in cubic feet 
per revolution will equal 0.4 the cube of the diameter in feet. 

184. Practical Rule for Power. — The delivered horse-power 
required for a given fan or blower is equal to the fifth power of the 
diameter in feet, multiplied by the cube of the number of revolu- 
tions per second, divided by one million^ and multiplied by one 
of the following coefficients: For free delivery jo, for delivery 
against one ounce of pressure 20, for delivery against two ounces 
of pressure 10. 

As an example showing application of rules, find the capacity 
in air delivered and horse-power required for a blower work- 
ing against a pressure of i ounce and provided with a wheel 5 
feet in diameter and of usual proportions, running at 300 
revolutions per minute, or 300/60 = 5 per second. 

The capacity equals (5 XsX5)(o.4)(30o) = 15,000 cubic feet 
per minute. 

The horse-power equals 

(5X5X5X5X5)(2o) (300X300X30 0) __ g^ 
1,000,000 60X60X60 '' 

If the speed should be doubled, the horse-power needed 
would be increased eight times, provided the relative resistance 
remained the same. It should be noted that the horse-power 
as given by the above rule is that delivered to the fan, and in 
reckoning the amount to be supplied, it should be increased 
an amount sufficient to cover any loss by friction in the motor 
and transmission mechanism. 

185. Tests Which Verify the Rules. — This extremely simple 
rule for capacity agrees very closely with an extensive series 
of experiments made on different fans, with proportions 
approximately those given. Thus, for instance, in a test 
made of a fan-wheel 5 feet diameter, running at 300 revolu- 
tions per minute at Wheeling, W. Va., the air discharged was 
16,446 cubic feet per minute against a pressure of about i.o 
inch. By the rule just stated the discharge would be 0.4 X 



382 



HEATING AND VENTILATING. 



i25X3C» = i5,ocx), an amount lo per cent less but still within 
the limits of error of measurement of air. In another test 
a fan of 4 feet 6 inches diameter when running at 310 revolu- 
tions gave a discharge of 11,651 cubic feet per minute under 
working conditions. The rules as stated above would give a 
delivery of 11,284 cubic feet per minute. 

In another case the test of an American blower-fan 18 
inches diameter, working against a pressure of i.i inches of 
water, delivered 1368 cubic feet per minute; by the rule given 
it should deliver 1394 cubic feet per minute. 

The simple rule stated for capacity, while approximate and 
applying only to fans of essentially the same proportions as 
those mentioned and when working under the conditions 
described, will still be found very useful. For fans of mater- 
ially different proportions working under higher pressures 
the rule will not apply even approximately. 

Experiments by the author with a fan 4 feet in diameter 
give the following coefficients for capacity and horse-power: 



Pressure above Atmosphere per 
Square Inch. 


Coefficient for 
Capacity. 


Coefficient for 
Horse-power. 


Inches of Water. 


Ounces. 


(a) 


(b) 




05 
1 .0 

1.72 

2.0 

3 74 



0.29 

59 
I.O 

1. 18 
2.0 


0.60 

.56 
•50 
.40 

•35 
.30 


0.30 
.27 

•25 
.20 

.16 

.10 



The table on page 383 gives results of tests of two fans 
used in heating the Veterinary Building at Cornell University. 

186. Relative Efficiency of Fans or Blowers and of Heated 
Flues. — Fans or blowers are usually driven by steam-engines 
of a medium or poor grade,, and as they must be considered 
in connection with the motive power for a fair comparison, 
they do not present the most efficient method of transform- 
ing heat into mechanical work. The very best engine con- 
structed would develop about a horse-power for a consump- 



MECHANICAL VENTILATORS. 



383 



Diameter of wheel, inches 

Width at centre, inches 

Diameter inlet, inches 

Discharge opening, inches . . . . * 

Diameter engine cylinder, inches 

Length of stroke, inches , 

Heating surface, lineal feet, total 

** '« <* *< heater 

'* '* tempering coil! 

Lineal feet per cubic foot heated 

Cubic feet of air per minute 

Lineal feet of pipe in heater, per cubic foot of air. . . . 

Pressure in ounces 

Revolutions engine per minute 

Revolution of fan 

Indicated horse-power 

Delivered horse-power, actually found 

Steam pressure, pounds 

Temperature outside air 

Temperature of room 

Temperature of warm air 

Heat supplied per minute B.T.U 

Heat per lineal foot of pipe, B.T.U. per hour 

Pounds of steam, per square foot of heating surface 

per hour 

Cubic feet of space heated 

Changes of air per hour 



Large Pan. 


Small Pan. 


36 


18 


54 


28 


40X42 


22X22 


19 


6 


8 


8 


4,770 


1,980 


3,816 


1,584 


954 


396 


12.7 


28.02 


21,000 


S.180 


4.5 


3-28 


0.875 


0.034 


220 


201 


200 


402 


8.6 


2.5 


5 5 


I-5I 


22 


22 


34 


34 


70 


70 


80 


136 


4,560 


5,180 


58.8 


195 -6 


0.17 


0.61 


121,724 


56,732 


lO.I 


5-5 



tion of 1.25 pounds of coal per hour under the boiler, which 
would correspond to an efficiency of transformation of heat 
into work of about 1 2 per cent. The engine ordinarily employed 
for driving blowers is of the simple non-condensing type, using 
about 40 pounds of steam per horse-power hour and requir- 
ing per horse-power from $ to 8 pounds of coal to be burned 
under the boiler per hour; its thermal efficiency is from 2 to 
4 per cent, perhaps averaging not far from 3 per cent. 

Quite an extensive series of experiments on different fans 
and blowers have been conducted by the author in Sibley 
College, Cornell University. These have shown that the 
efficiency of fans under usual conditions may vary between 10 
and 40 per cent, and under best conditions may rise to 50 per 
cent. 

A blower with an efficiency of 10 per cent, operated by 



384 HEATING AND VENTILATING. 

an engine having an eflSciency of 3 per cent, would constitute 
a plant with a joint efficiency of 0.3 of i per cent; this may 
be considered as the poorest case likely to be found in practice. 
The joint efficiency of engine and blower would probably be 
about 1.2 per cent in average practice, and about 2.5 per cent 
in the best cases likely to be found. In many cases all the 
steam exhausted from the engine may be used for heating or 
other useful purposes, which would make the joint efficienc)' 
from twenty to thirty times that mentioned above. 

The following mathematical principles may be applied: 
Thus let r equal that percentage of heat in the coal burned 
under the boiler which is converted into mechanical work by 
the engine, / that percentage of the indicated horse-power of 
an engine which is utilized in moving the air, R the total 
available heat in B.T.U., T and T the absolute temperature> 
inside and outside the chimney. 

The total useful work performed by a fan or blower will 

then be 

Wr^nirJR, (i) 

in which the efficiency of the engine and blower combined is 
denoted by r/. 

The ratio of the useful work done by the same coal in 
operating an engine and a fan to that done by heating a chim- 
ney for discharging air at the top will be found by dividing 
the above equation by the mechanical work done in a chimney 
(see equation (c), page 55, in which ^ = .238): 

W, 77&cTrf _i8s.2Trf 

^'^W, h IT' ^^ 

ist. Consider r/ = o.oo3 = the assumed lowest value, the 
outside temperature = 60°, so that r = 60+460 = 520 in all cases; 
then 

^' jj' (4) 



MECHANICAL VENTILATORS. 386 

2d. Take rf =0.012, the average value; then 

R,-Y (5) 

3d. Take rf =0.025 per cent, the highest value when the 
exhaust steam is not used ; then 

Rr-T (^) 

4th. For the case when the exhaust steam may be utilized 
or the fan can be driven by shafting, r may equal 80 per cent, 
/=35 per cent, and rf =28 per cent, for which case 

i?,=^ (7) 

From the above formulas it is noted that the relative 
efficiencies of fan and blower would be about equal for the case 
of the most inefficient fan and engine were the chimney 288 feet 
high; for the average case they would be equal when the 
chimney was 1155 feet high, and for the best case when the 
chimney was 2400 feet high. From this it appears that the fan 
and engine under average conditions are from three to twenty- 
four times as efficient as a chimney 100 feet high. In all the 
above cases the delivery of air from the top of the chimney is 
considered. 

A fan is frequently used to draw air by suction as well as 
to deliver it by increase of pressure; and as the air entering the 
fan is seldom heated to any great extent, the* work of a fan 
. imder usual conditions is fairly comparable with that of deliver- 
ing cold air into a chimney. For this case the ratios of efficiencies 
will be found by dividing formula (i) by formula (e), page 

RhT 
56, for supply of air to a chimney, We = -^ij^ ' 

Wr yjScr/r^ iis-2rfr^ 
^"We hT hT . ' . . W 



386 HEATING AND VENTILATING. 

When the outside temperature is 60°, T equals 520**, which wiD 
be used in all cases. 

Substituting r/= 0.003, we have for the most inefficient fan 
and engine 

^^ooo^ ^^^ 



Substituting other values of rj as before, values may be found 
for the average and best quality of fan and engine. For these 
last conditions the relative efficiency depends upon the square 
of the absolute temperature directly and on the height of the 
chimney inversely. 

Attention has been called to the extremely wasteful results 
which characterize the movement of air by heat, as in a chim- 
ney. From this it may be deduced at once that any mechan- 
ical appliance, even with a moderate efficiency, would be many 
times more economical for moving air than a chimney. This 
is rather more remarkable since mechanical appliances for mov- 
ing air at low pressures, as is usually required in ventilation, 
have a comparatively low efficiency and seldom make use of 
more than 25 per cent of the power applied. Even, however, 
considering the case when the efficiency is ver>' low, we shall 
still find the mechanical appliance usually much less wasteful 
for moving air than when heat is applied directly in a chinmey. 
Thus considering the case when the total efficiency of the heat 
aj)j)licd to drive a steam-engine and all the intermediate 
machinery for mechanically moving the air to be .6 of i per 
cent, we shall have the mechanical method of ventilation as 
many times more economical than the chimney as shown in 
the table on page 387. 

The foregoing discussion shows that mechanical ventilation 
as usually conducted is much more eflicient than that which 
may be obtained with heat applied directly to a chimney; 
consequently the cost of obtaining ventilation by mechanical 
means is many times less than by use of a heated chimney. 

*" ♦he truth of the conclusions regarding the relative 

Qation by mechanical means or b\- a chimney 



MECHANICAL VENTILATORS. 



387 



cannot be questioned when fuel has to be burned for this 
special purpose, yet it should be noted that in many cases a 
heated chimney is available without extra cost or, from the 
character of the building, is the only kind of ventilation per- 
missible; for such cases it is to be adopted as preferable to 
mechanical ventilation. 



TABLE SHOWING NUMBER OF TIMES MECHANICAL VENTILATORS 
ARE MORE EFFICIENT UNDER AVERAGE CONDITION THAN 
A CHIMNEY DISCHARGING AIR FROM A ROOM. 



Temperature 
of Chimney, 












• 






8o'» 


100* 


ISO" 


aoo" 


250* 


300" 


400* 


450* 


Fahr. 


















Height of 
Chimney. Ft. 








Ratio of ] 


Sfliciency. 








lO 


68.4 


73 4 


87.3 


102 


118 


135 


173 


194 


20 


34.2 


36.7 


43 6 


51 


59 


67 


86 


97 


30 


22.8 


24 5 


29.1 


34 


39 


45 


57 


65 


40 


17. 1 


18.3 


21.8 


24 


29 


34 


44 


48 


50 


13.7 


14.7 


15 4 


20 


24 


27 


35 


39 


60 


II. 4 


12.2 


US 


17 


19 


22 


28 


32 


70 


9.8 


10. s 


12.8 


15 


17 


19 


25 


28 


80 


8.5 


92 


10.9 


12 


15 


17 


22 


24 


90 


7.6 


8.1 


9 7 


II 


13 


15 


17 


21 


100 


6.8 


7 3 


8.7 


10 


12 


135 


15 3 


19.4 


125 


5-4 


5 9 


7.0 


8.1 


9 5 


10 


13 


9 


15 5 


ISO 


4.6 


6.1 


SI 


6.7 


8.0 


9.0 


II 


7 


13 


175 


3 9 


4-2 


50 


5.8 


6.7 


7 7 


Q 


9 


II. I 


200 


3-4 


36 


4-4 


51 


6.0 


6.7 


8 


6 


9 7 


250 


2.7 


2.9 


31 


41 


4-7 


54 


6 


9 


78 


300 


2.3 


2.4 


29 


3 4 


3 9 


4 5 


5 


7 


6.5 



187. Disk and Propeller Fans. — The same general formulae 
which have been quoted for centrifugal fans also apply to the 
disk or propeller fans. In this case the air is delivered from 
the entire edge of the blade and with a velocity proportional 
to the velocity of the blade at that point. An extensive series 
of tests of fans of this character were made by W. G. Walker 
of London, Eng., and published in Engineering, August, 1897. 
The results of the test show that the efficiencies under the 
best conditions are essentially the same as those for pressure- 
blowers as quoted. These fans developed, according to the 



388 HEATING AXD \^EXTILATIXQ. 

experiments made, a volumetric efficiency in some cases greater 
than unity; this can only be explained by the fact that the 
velocity of the air-partides must under some conditions have 
been greater than that of the blade, a condition sometimes 
found true in tests of propellers for steam-boats. 

The rule for capacity as given for blowers of the ladial-flow 
type would seem by the tests to also apply closely to propeller 
fans, while that quoted for horse-power required does not apph*. 
The capacity would be expressed by the following formula, in 
which a = a constant varj-ing from .06 to .50 per cent, dependent 
upon the resistance, 

The horse-power would be expressed by a formula, in which 
b=2L constant to be determined, 

188. Measurement of Air Siqiplied a Roooi. — Specifications 
for ventilating apparatus generally require as a condition of 
acceptance the delivery* of a specified amount of air into a 
room, and it is important that accurate measurements of such 
air be made. 

Air is generally delivered into a room through the grill of 
a register, and it will be found in nearly ever}' case that there 
is considerable variation in velocity in the air delivered from 
difl'erent portions of the register. The results would also vary 
considerably with the position of the anemometer, which is 
the best instrument for such measurements. An appro\'ed 
method of measuring the air discharged from a register requires 
the use of a temporar>- pipe or tube of the size of the register 
frame, which b extended into the room for a distance of about 
two feet, and is subdivided into small sections, each from 4 to 8 
inches in size, by fine wres. The average velocity if taken in 
each section with the anemometer will represent accurately 
the velocity of the entering air. and this quantity multiplied 
by the area of cross-section of the temporar>- tube will give the 
volume supplied. 



MECHANICAL VENTILATORS. 389 

If the anemometer is held close to 'the face of the register, 
there may be considerable error in obtaining the average velocity 
and also the actual area of cross-section of the incoming air, 
both of which quantities are essential. 

189. Introduction of Air into Rooms. — ^The principal dif- 
ficulties experienced in mechanical ventilation are those relat- 
ing to an equable distribution of air in the rooms to be ventilated. 
It is a comparatively easy matter to force any required amount 
of air through a given duct into a room provided there be 
suitable discharge-flues or openings leading to the air, but it is 
a very diflScult matter to supply this air in such a manner that 
it will be thoroughly and perfectly distributed. In all cases 
of mechanical ventilation there must be erected ducts or pipes 
for conveying the air to the room, and also suitable ducts or 
passages for removing the air from the room, and these may be 
arranged in various ways with reference to each other. 

Air may be introduced into rooms through registers either 
in the floor or ceiling or in the side walls at various heights, 
and each system has certain advantages and disadvantages. 
In introducing the air through floor-registers, any sweepings, 
dirt, or contamination falling to the floor is likely to be carried 
by the entering air into a position where it might be respired 
and thus become a medium for spreading or conmiunicating 
disease. Where warm air is introduced for ventilation, as is 
likely to be the case during the cold months, there is a tendency 
for this air to rise, thus causing a natural circulation, which 
assists the artificial one due to pressure. On the other hand 
natural circulation tends to increase the air-currents in local 
positions, and especially in the lines between the supply- and 
discharge-registers, and this prevents that equable distribu- 
tion which might otherwise be obtained. This system, which 
we may term the up-draft system, has been extensively used 
in the past, and is at the present time frequently employed for 
the ventilation of large auditoriums, as, for instance, the House 
of Parliament in London, Eng., the Senate Chamber at Wash- 
ington, D. C, and various theatres and opera-houses. In the 
House of Parliament, London, Eng., the air is introduced through- 



390 HEATING AND VENTILATING. 

out the whole floor-area through small perforations covered 
with matting, and is removed through registers in the ceiling. 
Professor S. H. Woodbridge constructed a system of ventila- 
tion, in 1896, for the Senate Chamber at Washington, in which 
the air is introduced through perforations located in the fixed 
furniture, and discharged in the ceiling. 

The introduction of the fresh air through registers or per- 
forations in the ceiling and its discharge from the floor-line 
would seem to be supported by the best theoretical reasons, 
since it naturally presents the best methods for an equable dis- 
tribution, provided the air-currents are not of sufficient intensity 
to cause a sensible draft. This system has not, however, been 
as extensively used as that with the up-draft currents, but has 
been applied successfully to a few large auditoriums. 

The introduction of air from the side walls is perhaps more 
extensively practised for the ventilation of rooms of moderate 
height and extent than any other, and is doubtless the best 
suited for the ventilation of such rooms as are usually found in 
school buildings. For such cases the best results are obtained 
by locating the supply-register on an inner wall of the room 
and about three or four feet from the ceiling, and the discharge- 
or vent-register in the same wall and near the floor-line diagonally 
opposite the supply-register. This arrangement of registers is 
found to give a fairly equable distribution of the air with rooms 
from 12 to 14 feet in height when not exceeding 30 to 40 feet 
in floor dimensions. The introduction of air at two or more 
registers under similar conditions is likely to cause cross-cur- 
rents and eddies, thus producing irregular ventilation. In 
all systems of ventilation, as previously mentioned, the fresh 
air should be introduced in such a manner as not to produce 
sensible drafts; where it enters in such a position as to impinge 
directly on the people, the velocity should, for best results, 
not exceed 3 feet per second; but where it is delivered in the 
upper portion of the room and into a larger body of nearly 
still air the velocity may be 6 to 10 feet per second without 
producing serious inconvenience to the occupants. 

Mechanical ventilation may be performed by forcing the 



MECHANICAL VENTILATORS. 391 

required amount of air into a room and allowing it to discharge 
through suitable flues; or by exhausting the air from a room, 
fresh air being supplied by suitable connections to the outside; 
or it may be performed by a combination of forcing and exhaust- 
ing methods. The system of forcing the required amount of 
air into a room is as a rule more positive than that of exhaust- 
ing the air from a room, since in the first case leaks in the flues 
or conduits have less influence on the results than in the other; 
this system is also generally more cheaply constructed. The 
exhaust system would necessarily be used in cases where noxious 
gases need to be removed from a room without the possibility 
of spreading into adjacent rooms. The combination of the two 
systems is frequently employed ; in which case the air is delivered 
into the room by force or under a slight pressure and is removed 
from the room by action of an exhaust-fan placed in the dis- 
charge-flue. In this latter case the exhaust fan is virtually 
used as a substitute for a chimney. 



CHAPTER XV. 



HOT-BLAST HEATING. 



190. General Remarks. — In the systems of hot-air heat- 
ing which have been described the circulation of air caused 
by expansion due to heating, which is a feeble force and is 
likely to be overcome by adverse wind currents, by badly pro- 
jx)rtioned pipes, or by friction; by employing a fan or blower 
of some character for moving the air the circulation will be 
rendered positive and strong enough to overcome these dif- 
ficulties. 

This system can be employed where power is available, 
and in many cases will be found to present an economical and 
satisfactory system of heating, comparing well with any that 
has been devised, especially when the amount of ventilation 
provided is considered. The cost of heating a large quantity 
of air is, however, in every case one of considerable amount, 
so that it is quite probable that in expense of operation no 
system of indirect heating, whether by furnace or steam-pipes, 
can compare with that of direct hot-water or steam radiation. 
The system of mechanical ventilation is in almost every case 
employed in connection with steam-heated surfaces, but in 
some instances the system has been applied successfully with 
furnace-heated surfaces. 

191. Various Forms of Mechanical Ventilating and Heating 
Systems. — A mechanical system of ventilation is much more 
economical than one which depends upon the use of a heated 
flue for the reasons already given, and in connection with 
a method of warming it may also form a convenient and 

392 



HOT-BLAST HEATING. 393 

economical system of heating. In general it will be necessary 
to warm the air which enters for ventilation purposes in cold 
weather in order to prevent uncomfortable sensations of chilli- 
ness; this may be done to a sufficient extent to provide all the 
heat needed for warming or to an amount sufficient only to 
prevent a sensation of chilliness, which may be perhaps to 
72° to 75°. A mechanical system of circulation can be employed 
for the purpose of heating only, by driving air over heated 
surfaces and thence into the rooms to be warmed, and many 
successful plants of this kind have been erected for heating 
shops or other places where direct radiation was objectionable; 
it is most successfully used, however, in buildings where ventila- 
tion is necessary by introducing a constant volume of air which 
is heated more or less as may be necessary to provide a uniform 
temperature in the room. 

Systems of mechanical ventilation and heating have been 
used in the art for more than a century, but until within the 
last decade they have not been extensively or systematically 
installed. 

As erected at present we have the following general 
methods of installation in use. First, systems which supply a 
constant volume of air which is warmed sufficiently to provide 
all the heat required; the air may be warmed (A) by concen- 
trating the heating surface near the fan and providing a flue or 
passage over it for hot air and another around it for cool air; 
these two flues or pipes are kept separate for some distance, but 
join at the bottom of a vertical flue leading to the room to be 
heated, where they are controlled by a regulating damper, 
which is arranged to open one flue as it closes the other; this 
system is generally known as the double duct system, and 
has been extensively used. All the air before reaching the 
fan is usually warmed to 70° or 75° by a coil of steam-pipe, 
termed the tempering-coil. The air is warmed in the second 
way (B) by separate radiating surfaces arranged as for indirect 
heating with steam ; at the base of the vertical flues leading to 
the various rooms to be warmed, a by-pass pipe around the 
heater permits the cool or tempered air to enter a room in any 



894 HEATING AND VKNTILATING. 

desired amount, being regulated by a damper. In this latter 
system the heating surface is subdivided, but only one air-pipe 
has to be erected from the fan to each heater. 

A third system (C) has been recently used to a considerable 
extent, in which the air driven into the room by the fan is 
warmed only to a temperature of 72° to 75°, or sufficient to 
prevent a sensation of chilliness, and the remaining heat needed 
is supplied by direct radiation. For this latter case sufficient 
direct radiation must be used to balance the loss from the walls 
and windows, or in other words, the steam-radtating surface 
for each room in square feet must equal 

in which G = area of the glass in square feet, W equals the 
area of the exposed surface of the wall. 

The system employed for heating and not for ventilation 
would need the same amount of radiating surface and piping 
or ducts for supplying hot air, but would not need the pipes for 
supplying cool or tempered air. 

In all these sjstems a fan or blower, as described in the 
previous chapter, is located in a cpnvement place, but usui 
in the basement; it can be arranged to draw by suction (ff tj 
force the air over the heating surface as desired, but i 
ventilating systems with double ducts or heaters at the b 
the flues, it is in general more convenient to force the s 
the main heater or heaters and draw the air by suction 1 
a steam-coil situated between the fan and the < 
knoun as a tempering coil and of sufficient extent to ^ 
entering air to 70° in the coldest weather. 

The usual arrangement of fan and heatT" 
the heater is concentrated at one place, is 
The entering air is lirsl drawn through a fi 
dust, if necessary, thonce through a ten^ 
not shown in thi.' drawing. It ihcn passes 
is thonco in jiart forced through the he 




HOT-BLAST HEATING. 395 

hot-air chamber, from which hot-air pipes lead to vertical flues 
leading to the various rooms; a part flows into the passage 




beneath the fan and thence into the cold or tempered air-pipe, 
which in the system shown is directly below the hot-air pipe, 
although in other systems the position may be reversed. In 



HEATING AND VENTILATING. 



Fig. 258 is shown another style of blower and heater in whid 
the cold-air flue is located above the hot-air flue. 




Fic. 158. — Arrangemenl of Bbwt 



192. Volume- or Regulating-dampers. — These dam^ 
used at the place where the horizontal flues for hot and cd 
air join a vertical flue leading to the room to be warmet 
These dampers are made in a variety of ways, but iU 



I 




Fig. 359. — Regulaiing-dampers. 



Fic. 260.— Volui 
dampers. 



such 3 manner that one flue will be opened as the c 
closed, so as to provide the discharge of a constant vol 
of air. 

One form of damper is shown below consisting of two plai 



HUT-BLAST HEATING. 



397 



I 



or disks mounted at right angles on the same shaft and so 
connected that the hot-air pipe will be closed as the cold-air 
pipe is opened and vice versa. The damper in the figure is 
shown as operated by a thermostat, but it could readily be 
arranged to be operated by hand from the room to be 
warmed. 

Another form of volume damper is also shown of the same 
general character, and operated in the same manner and so 
as to secure the same results. 

153. Form of Steam-heated Surface.— The heating sur- 
face is generally built of inch pipe, set vertically into a square 
cast-iron base, connected at top with return-bends, although 
the box coil, or any form 
of indirect radiating surface 
could be used. 

The three following 
trations show forms of i 
ing surface built up of 
inch pipe in use in 
blower system of hea 
The heaters are espe( 
designed to afford free _ . 
culation of the steam and 
to permit a ready removal 
of the water of condensation 
and air. 

The heating surface will 
emit 600 to 1000 B.T.U. per square foot per hour and 
should average i square foot for every 13 to 15 cubic feet 
of air heated from 0° to 120° F. per minute. To account 
for inefficiency of heating surface there should be about 10 
per cent excess or one square foot of heating surface for 
12 cubic feet of air heated. This heating surface for con- 
venience is usually estimated in lineal feet of one-inch pipe, 
and on this basis there should be i foot in length of one- 
inch pipe for 4 cubic feet of air heated per minute, which 
agrees well with the average practice ; the increase in tem- 




FiG. :6i. — Healer for Mechanical System. 



HEATING AND VENTILATING. 



perature of air is as shown in the following diagram, Fig. 364, 
as the results of tests previously referred to. 




Fic. 161.— DeUuIa of Heatet Shown in Fig. 161. 

Cast-iron Healers. — Formerly, nearly all the heaters used 
to warm or heat air for mechanical ventilating and heat- 
ing systems were constructed of one- 
inch wrought-iron pipe. Heaters con- 
structed of cast-iron sections are now 
used and give good results both as 
to efficiency and capacity. Cast iron 
possesses the advantage over steel or 
wrought iron of being more durable 
and less expensive, and will doubtless 
be employed extensively in future in- 
stallations. 
1^0 *.,^lfa,c, lo, Me- Flaes -Registers.-- 

ihannal Sysltms o( Healing. yn " b 

The dimensions of the ducts or flues 
leading from the heater should be such that the required 
amount of air may bo delivered with a low pressure and 
velocity, so as to av<)i<l cxcessi\u resistances due to friction. 
The \'clocity which will be producc<i by various pressures in 
excess of that of the almospherc is given in Tabic XXVI, from 




HOT-BLAST HEATING. 399 

which it is seen that a drop in pressure sufficient to balance } 
inch of water (0.29 ounce per square inch) will produce a 
velocity of 30 feet per second in a pipe 100 feet long and i foot 
in diameter; this is generally considered to be the maximum 
velocity which should be permitted in any of the pipes or pas- 
sages. In proportioning apparatus in this system of heating 
it is generally required that sufficient air shall be brought in 
to change the cubic contents of the room four times per hour. 









r 


««. 


.^» 


.„.. 


.„ 


,.. 




























1 


































'. 




























1 




■- 
















,-« 


^ -■ 


'"■ 


















\^ 


'> 






»;• 


S"." 


w 












Jr 












r u.n 


^ 


'7i"t 


...L. 


I 




> 

























































u 


m 


a 


— 


^ 


' 


^! 


-- 







-+ 




ij 



-I 



Fig. 264. — Diagram showing Relation between Temperature of Dis- 
charged Air and Heating Surface. 



A more accurate method of proportioning area of ducts is by 
use of Table XXV, which gives the diameter of a round pipe 
or side of a square pipe required to discharge a given volume 
of air at a known distance and with a drop in pressure of one 
inch of water. The author would advise the use of this table 
in proportioning ducts for supply of air, and in its use it is first 
necessary to determine the air required for each room, and the 
length of the pipe-line. This method will insure equal resist- 
ance in the various pipe lines and an equable distribution. 

The pipes are usually made of galvanized iron or bright tin 
and should have tight joints and be protected from loss of heat 



400 HEATING AND VENTILATING. 

by some good covering. Flues of brick or masonry cause more 
friction than those of galvanized iron, and if used should gen- 
erally be about two inches larger in diameter than provided 
for by this table. As branch pipes for various apartments 
are taken off, the main pipe can be reduced in size; this should 
never be done abruptly, but only by the use of tapering tubes, 
the angle of whose sides measured from the line of the main 
pipe should rarely be greater than 15 degrees. In a double- 
duct system of heating the area of the hot-air duct should be 
sufficient to carry 90 per cent of the total air; that of the cold- 
air duct sufficient to carry 40 to 50 per cent. 

The area of the cold-air duct or passageway leading to the 
fan should be as great as possible in order to keep the velocity 
of entering air low; if the area of cross-section is equal to the 
sum of the areas of all the ducts leading from the heating surface, 
the velocity will probably be about three-quarters of that in 
the hot-air pipes, and may draw in considerable dust and dirt 
from outside. Except in very large rooms the flues which con- 
vey air should discharge near the upper part of the room. 
The friction in small pipes is greater than in large ones, being 
relatively proportional to the curcumference or perimeter; 
hence the sum of the areas of the branch pipes should be con- 
siderably greater than that of the main.* 

The table on opposite page gives the number of small pipes 
which provide an area equivalent to that of one large pipe of 

* The velocity of flow of air is given in formulae in Chapter V; the amount 
discharged is equal to the area of the pipe multiplied by the velocity and will 
be equal in every case to the square root of the fifth power of a constant multi- 
plied by the diameter of the pipe. If we denote diameter of larger pipe by Dj 
of smaller pipe by d^ and the number of smaller pipes required to make one of 
area equivalent to that of larger by n, 



'-&■ 



To find diameter of round pipe, (/, which shall be equivalent in carrying capacity 
to a rectangular pipe with dimensions a and 6, wc would have 






HOT-BLAST HEATING. 



a 

g. 

u, 
O 

S 

Q 
Id 

E 

1 
1 

2 


s of the branch pipes. 

e figures In any horizonlal line give ihc number 
of pipes, of tin; diuincter given at the lop of the 
column, that will be equal in capacity for 
conveying air lo the one given c^posite 
in Uie first column. Thu3 one lo- 
inch pipe is equivalent in carrj- 
ing capacity, friction in- 
cluded, to 3-6. 6-indi 
pipes. 


IS- 


Is-': 


is::: 


ls?-n 




is:!-^:-; 


Is-:n;:; 


!«*„.:..„ ,101^0 


ls::-::a°:= 


1 »^ _ - ^ » 4«« 








sjr:-„.^:;^i--" 


W 1- 




^.= Is: 




i \^--: 












fs:r; 








=,^*«^^«o«»»^-5^ 


















r-----"" 














;22J^Sffft?,5S?Sff 






*" """'•""*"=^ 






S 3'5 S= :; S;S i^gg g ?£ ^ 1 


|,';";;t*=--"»'>'=i»'"--i:53slH 


U.i'S,*^"""""'-- 


^sssj^a^-c'^sg^s^ 


|«^™-"*"~"2:=«l 


l^^r-.si'^l^lggg 


|„~5=,!iS5^3SS5^Sft| 


IsfHIifllllii 




a -«w.r«»^as»o-«i*»«=w 


^SSSS?iSSSS£S:ZS 


a 





402 



HEATING AND VENTILATING. 



similar cross-section; in case no table is at hand the same 
results may be obtained by dividing the larger diameter by the 
smaller one and taking the square root of the fifth pK>wer of the 
quotient. 

The following table gives the actual amount discharged 
with constant resistance, and with loss of pressure equal to one- 
half inch of water column in round pipes, as computed from 
Unwin's formulae. (Also see Table XXV, Appendix.) 



VELOCITY AND QUANTITY OF AIR DELIVERED IN PIPES OF DIF- 
FERENT DIAMETERS, EACH 100 FEET LONG, WITH AN AIR- 
PRESSURE EQUAL TO i LNXH OF WATER COLUMN. ' 



Diameter of i 


Velocity of 

Air. Ft. 

per Sec. 


Cubic Feet of 


Diameter of 


Velocity of 

Air. Ft. 

per Sec. 


Cuhic Feet of 


Pipe. In. 


Air per Min. | 

1 


Pipe. In. 


Air per Min. 


I ' 


8-7 


..6 ;i 


16 


35 6 


3.024 


2 


12.4 


16 ■! 


18 


36-8 


4.032 


3 


15 o 


45 


20 


38 8 


5,184 


4 


17-3 


90 ,; 


22 


40.6 


6^80 


S 


19 4 


160 ; 


24 


42.4 


8,208 


6 


21.3 


253 


26 


44 2 


9.036 


7 


23.0 


3SO 


28 


46.0 


".952 


8 


245 


515 


30 


47.4 


14.256 


9 


26. 1 


720 


36 


52.0 


23.040 


lO 


27 4 


900 


42 


56.1 


33.120 


II 


28 6 


IIQO 


48 


Of .0 


46,080 


12 


30 5 


1440 


54 


63 6 


6l,Q20 


13 


31 3 


I()20 1 


60 


67.0 


80.640 


14 


32.4 


2160 









Air which is drawn in from outside at high velocity is often 
loaded with dust, and for this reason filters made of some tex- 
tile material, or bafHe-plates which discharge the dust into 
vessels of water, are sometimes required in the passageway 
leading to the fan. 

The net areas of registers should be sufficiently great to 
prevent the velocity in the entering air becoming so great as 
to produce a sensible draft. Taking this limiting value at 5 
feet per second, the area of the register can be computed. 
If the air is to be changed four times per hour, there should be 
34 square inches in the register for each 1000 cubic feet of space. 



HOT-BLAST HEATING. 



403 



The nommal area of the register should be about 50 per cent 
greater than given by this computation; the actual areas of 
commercial registers is given in table, page 340. 

195. Blowers or Fans.— The principles relating to the 
operation and construction of fans and blowers have been quite 
fully given in the preceding chapter, together with a descrip- 
tion of the more important types, so that it is only necessary 
in this place to refer to such features of construction or opera- 
tion as are peculiar or of special importance in connection with 
systems of mechanical ventilation and heating. 




Fig. 165, — Blower Connected lo Engine 



The motive power employed to drive fans may be obtained 
from a running countershaft, from an engine either directly 
connected or belted, or from an electric or water motor. Where 
the fan is to be used only at intervals, the electric motor will 
be found more desirable and fully as economical as the engine. 

Where fans are used in connection with heating systems 
they can usually be driven most economically by a steam- 
engine, arranged so that the steam after passing through and 
driving the engine will exhaust into the heating coil. For 
this condition the cost of motive power will be scarcely appre- 



404 HEATING AND VENTILATING. 

ciable, since the loss of heating capacity by the steam in pass- 
ing through the engine will not usually exceed ten to thirty 
per cent. 

The fan should be located in a position where the noise 
caused by its operation is likely to be of little importance, and 
il should be arranged so that a portion or all of the blast can be 
dcflcctwl from the heating surface and sent to the rooms with- 
out being wanned if so required. This can be done by prop« 
construction of ducts and dampers. 

An exhaust fan in the ventilating shaft has been used, in 
some instances with good results, for remo\-iag air from a 
building and producing circulation over the heater, but there is 
liabilit)' of leakage or infiltration of air into, the flues from the 
outside. lu case air enters this without passing ovez the heat- 
ing surface, it is likely to reduce its efficiency, so that in prac- 
tice it has not proved as satisfactory- as the pressure-sys- 
tem. For purposes of TCOtilation only, or (or the removal of 
foul And noxious gases where the ventilating ducts are tight. 
or as on accessory- to the pressure^sj-stem, the exhaust fan is 
\tiy dikicut and often in%-aluable. 

tg6. HeatiDg Surface Required. — The nketbods of pro- 
portioair^ (he beating surface will be the same in every par- 
ticular as tbo^e previously deiscribed for indirect bcatos, 
and for hot-air fumaccs. In this case. bowe\ier, 
passes over the beating sunaces with i 
the amount cS heat wlucb ts given off b nuny t 
that from onlinar>- raulialins sui&kcs in ifiicct I 
■MSits ^Iraw that Ibe number oC beat-units given ^^ 
dSfefcace of tvtapcnture per square toot o: f ^-::^.:c per boo* ' 
dc|KMlnit on a functioQ of tbe sqtiarc txxtt ^ : the vdoc' 
tbe air m Ceet per second; u: ^ \i-A-»ity oi iO i«i pr 
this might amoont to 6 h^.: -nij^ For very ai' 
the difletCBce of tenperat_: . • ^v^ beaiiag mr' 

^ve^,aC ptr sqfwit fioM > : .xo )■ 

etfinvlait o( tkat gmn ». ~ . 
MMcHaa t pMMdofslcaa 




HOT-BLAST HEATING. 405 

The following general formula will apply to this case: 
Let r= temperature of heating surface, / that of the air of the room, 
/' that of outside air, /" that of air leaving heating surface, d the mean 
temi)erature of air surrounding heating surface=§(^"— /'^, n^nxmiber 
of times air is to be changed per hour in the room, C cubic contents of 
room, a = coefficient giving number of heat-units per degree difference of 
temperature per square foot per hour from heating surface. We have, 
since one heat-unit is capable of heating 56 cubic feet of air one degree:* 

Cubic feet of air heated per hour =«C; 

nC 
Heat-units required for warming this air =— rC^"— O; 

50 



Square feet of heating surface 



56(i(r-/i)' 



Substituting in the last equation 

a(r-/i) = iooo; /"-/' = 70, 

and multiplying by 60 to reduce to minutes, we have 

nC{t'' - /O60 (nC) (70) (60) _ nC 
S6a{T'-l') "" 56X1000 ^13.3' 

From this computation it would appear that one square 
foot of heating surface would warm 13.3 cubic feet of air 70^ 
per minute. In designing it is considered safe to reduce this 
to 12 cubic feet, as 3 lineal feet of one-inch pipe are practically 
equivalent to one square foot of heating surface; we note from 
the above that one fool of one-inch pipe in the heater will warm 
4 cuhic feet of air per minute, 

197. Size of Boiler Required. — From the preceding state- 
ment it is seen that one square foot of heating surface in 
mechanical heating will condense from 0.5 to 0.8 the amount 
of steam that can be produced by one square foot of heating 
surface in the boiler. Hence there should be from 0.5 to 0.9 
as much area of heating surface in the boiler as in the indirect 
heater, or, in other words, there should be one boiler horse- 

♦ See Table X, temp, at 70** F. 



406 HEATING AND VENTILATING. 

power for every 20 to 30 square feet in the heater. The propor- 
tions of grate surface, chimney, etc., will be found by con- 
sulting Chapter VIII. 

198. Practical Construction of the Hot-blast System ci 
Heating. — The following matter regarding the construction of 
mechanical heating plants has been kindly furnished for this 
book by Mr. F. R. Still of Detroit, who has had an extensive 
engineering experience in this particular kind of work: 

Air Required. — The following is intended to give the basis 
of calculation for different parts of a plant of a mechanical 
heating system. The first thing to consider with this system 
usually is the amount of air to be delivered and warmed per 
minute. Experience has proved that the delivery of an amount 
of air at 120° into a building or apartment equal to its cubic 
contents every 15 minutes, will warm it under average condi- 
tions of construction of 70° F. when the outside temperature is 
zero. This amount of air will accomplish like results in some 
buildings when the outside temperature is 10 or even 20 degrees 
below zero, and in other cases this amount will be found insuf- 
ficient, the variation being due to construction, glass surface, 
and other conditions. In some classes of buildings, for instance 
churches, school -houses, theatres, and hospitals, a change of 
air may be required every 10 minutes. 

Amount of Heating Surface. — Having determined the 
amount of air required, the next consideration is the amount 
of heating surface to be used in the indirect heater. This can 
be treated better by taking a specific example; for instance, 
suppose that 20,000 cubic feet of air to be delivered into the 
building every minute (1,200,000 cubic feet per hour) at a 
temperature of 120 degrees, when air outside is zero, that the 
steam-pressure on the coils or heating surface is 10 pounds per 
square inch, and that the temperature of the water of condensa- 
tion is 213 degrees. In one pound of steam at a pressure of 
10 pounds above the atmosphere there is 1 186.5 units of heat, 
while in one pound of water of condensation there is 213 
units, leaving 973.5 units, which is given off by the heating 
surface. By consulting Table X it will be seen that at tem- 



) 



HOT-BLAST HEATING. 407 

perature of 70® F. one heat-iinit will warm 56 cubic feet of air 
one degree, and hence to heat one cubic foot 120 degrees 
will require 2.15 heat-units; each pound of steam gives off 
973.5 heat-units and will heat 452 cubic feet of air from zero 
to 120 degrees. To heat 1,200,000 cubic feet of air to 120 
degrees will require 2660 pounds of steam. The indirect 
heater provided with blower will condense imder average 
conditions i pound of water per square foot of surface per 
hour, and hence we should require as many square feet of 
surface as the quotient of 2660 divided by i, or 2660 square 
feet. 

Size of Boiler. — To find the size of boiler needed, divide the 
total steam required per hour, in the example 2660, by that 
required for one boiler horse-power; this, when water of conden- 
sation is all returned to boiler, is 34.5 pounds, and we obtain 
77 horse-power. This computation gives a larger boiler than 
would generally be installed for work of this magnitude. The 
rated horse-power of a boiler is capable of considerable increase 
in times of necessity and for short periods; It can hardly 
be considered good practice to overwork a boiler, but as extremely 
severe weather is usually of very short duration and the balance 
of the season mild, there is good reason, on the score of economy 
in first cost, for this practice. The boiler is usually rated on 
the supposition that it will need to supply 1.5 pounds of steam 
for each square foot of surface in the radiator per hour, in which 
case 23 square feet of surface would be supplied by one boiler 
horse-power. This estimate would require the normal rating 
of the boiler to be developed during the average stress of weather; 
this method would require a boiler of about 60 horse-power for 
the plant considered in the example. Such a method of pro- 
portioning has proved quite satisfactory in actual practice, 
although greater economy could, no doubt, be obtained by 
using a larger boiler. 

Size of Blower. — We are next to determine the size of 
blower required to deliver 20,000 cubic feet of air per minute 
under a pressure of one inch of water, which is about the pres- 
sure ordinarily used for such a case. This pressure corresponds 



408 HEATING AND VENTILATING. 

to a peripheral velocity of 4000 feet per minute. Then for a 
steel plate blower 

4ooo = TZ?iV^, 
£>.V = i274. 

199. Description of Mechanical Ventilating Plant — ^The plant 

erected in the New York State Veterinary College in 1896 
is described, not because it has any peculiar points of merit 
or is to be regarded as a model of its kind, but principally 
for the reason that the author has in his possession data regard- 
ing details of construction, and has had careful tests made 
of the efficiency of the plant. 

The buildings are arranged as follows: A main building 
three stories in height, in which are located the offices, lecture- 
rooms, museum, laboratories, and, in the basement, the heat- 
ing and ventilating plant; the north wing to this building, 
one story in height, containing the anatomical theatre, labora- 
tory, preparation room, locker, and lavatory; a mortuary 
building located in the rectangle formed by the main building 
and north wing at two sides; an operating shed east of the 
mortuary-; and the stables and the isolated wards for con- 
tagious diseases, which are located to the east and south, and 
not heated from the main plant. The operating shed is built 
of wood; all other buildings are of buff brick and of slow- 
burning construction, viz., all the inner walls are finished in 
brick and painted, the timbers are all extra heavy and exposed 
to view, the flooring and sheeting on the roof is laid over 
plank, the ceilings are of narrow pine, and 5n general no enclosed 
spaces are left. The roofs are all covered with tin and the 
trimmings in the interior of the main building are of oak. The 
building is lighted, except in the north wing and operating 
shed, through side windows; in the former the principal light 
comes through skylights in the roof. Except on the three 
stories of the main building, all floors are of concrete. ' A 
vault in the rear of this building and on a level with the base- 
ment contains the boilers, crematory, and cold storage. 



HOT-BLAST HEATING. 



409 



The exposure of walls and windows to the weather is about 
as follows: 



Main Building. Brick Wall. Glass. 

On the north about 3366 sq.ft 644 sq.ft. 

south 3366 ** 644 ** 

east 9339 ** 1546 ** 



< ( 



n 



It 



it 



west 9504 

Surfaces covered by tin roof 6074 ** 



1572 



<( 



North Wint. Brick WaU. 

Total exposed wall surface 6069 sq.ft. 

* * roof surface 4875 

Skylight surface 552 

Window surface 1 70 



< < 



(( 



ti 



The essentia] dimensions are as given in the annexed table: 

DIMENSIONS OF PRINCIPAL ROOMS AND FLUES. 



Room. 



First Floor. 



No. X *.... 

No. a*.... 

No. 3*.... 

No. 4 

Museum . . . 
South Hall . 
North Hall 

No. s 



Second Floor. 

No. 8 

No. 9 * 

No. II * 

No. 12 * 

Museum and Temp. \ 
Lecture- Room . . . . j 

South Hall 

North Hall 



Third Floor. 



No. 13 *. 
No. 14 *. 
No. IS. . 



No. 16. 



No. 17 * 

No. 18 

North wing, first floor. 

No. 6 

Closets, and lockers. 
No. 7 



Cubic 

Contents 

Cu. Ft. 



4.920 

3.600 
4.920 
3.600 
39.366 
7.200 
7.200 

20,800 



5.904 

5. 904 
5.904 
5.904 

34-992 

3.600 
3.600 



.'^.904 

5.904 

20.892 

13.488 

5.904 
5. 904 

39.600 



Number 

of 
Persons. 



Air-flue. 

Dimensions 

Inches. 



10 

10 
10 
12 
10 



135 



12 

10 
10 
10 

10 



40 

10 
10 



40 
10 



8X7JH 
6X7|T 



o 
o 
o 



/•3(8X24\ H 
\ 3(6X24/ T 



{ 



8X7J H 
6X7iT 



10 
10 
40 



1 1 



o 
o 



(8X7} 
l6X7i 

,(8X8) 
^(8X6) 
,(8X8) 
^(8X8) 
8X7J 
6X7i 

3(16X24) 
3(16X20) 



Air- 
register. 
Inches. 



lOXiS 

loXis 
loXis 
loXiS 



4(21 X29) 



12X10 

14X20 
12 X20 
14X20 



14X20 
14 X20 
2(20X24) 

2(18X24) 

12X24 

14X20 
3(16X24) 
3(16X20) 

2(10X16) 



Vent, 
register. 
Inches. 



8X1S 

8X1S 
8X1S 
8X1S 



2(24X24) 
2(24X16) 



10X20 

10X20 
10X20 
10X20 



o 
o 



10X20 
12X20 

2(18X21) 

r 18X20 
\ 18x21 

12X20 

12 X20 
3(16x20) 
3(20x24) 

10x16 



Direct 

Radi- 

atin 

Sq 



!%. 



40] 

40 

40 

40 
240 
110 
100 

80 



40 

40 
40 
40 

240 

o 
o 



40 
40 

100 

100 

40 
40 

400 

80 



* OflSces and studies assumed as containing 10 people. 



410 



HEATING AND VENTILATING. 



Description of Plant. — ^The ventilating plant is located in 
the basement, and as shown on pUm and sectional views, con- 
sists of two independent heating and ventilating plants con- 




nected to different portions of the building. These plants 
were installed so that if one portion of the building only was in 
use, the other portion need not be ventilated. A system of 



HOT-BLAST HEATING. 



411 



direct heating was put in for the halls and museum and some 
rooms when no ventilation was required for supplying heat 
It was also put into a number of other rooms to be used after 
school hours, when the ventilating system would not be in 
operation. This system, although shown on the drawings, is 
of no especial interest and was only erected because of the 
peculiar conditions which existed. 

The cold air enters the building through two windows; 
from these it is carried to the cold-air rooms shown on base- 
ment plan, and before entering which it is passed through fine 




LONGITUDINAL ELEVATION 
Looking at Front Wall 

Fig. 267. — Elevation Showing Direct Radiation. 



wire screens to remove any large particles of dust which might 
be drawn in. Air from the museum, which is usually unoccu- 
pied, can also, when desired, by the opening of certain registers, 
be drawn into each cold-air room and mixed with air from the 
outside. From the cold-air rooms it is drawn into the fans 
through a coil of steam-piping known as the " tempering 
coil,*' the office of which is to warm or temper all the air enter- 
ing the building to between 65° and 70°; in case the enter- 
ing air is already near this temperature, the damper is so 
adjusted that the entering air passes underneath the tempering 
coil and through the by-pass. 

The air-pipe from each fan, and through which the air is 



412 



HEATING AND VENTILATING. 



forced, is separated into two pipes, one above the other. Tlie 
upper and larger one contains a chamber in which is placed a 
number of sieam-coils similar to the tempering coil. This is 
called the heater, its duty beii^ to raise the temperature of the 
air passing through the warm-air pipe from 65" or 70° to 100" 
or 150°. 

The general arrangement of the system is shown in Fig. 
366. from which it is seen that air is taken in from the outside, 




Fig. 268. — Speed, Horse-power, and Weight of Air, Large Fan, 

Feb. 15, 1897. 



is passed through or under the tempering coil T. depending 
on the position of the damper. This dami)er may be regulated 
as desired, cither by a thermostat or by hand. The blower is 
placed as shown, and ser\cs to draw in the air from the out- 
side, also to force it over the heating surface and into the 
warm-air chamber, also through an oi>ening in front of the 
healer and into the cool-air chamber. I-rom the warm-air 
chamber and also from the cool-air chamber pipes are led to 
a vertical flue (which we will term the mixing flue), connecting 
with the rooms to be heated. These pijjes are controlled 



HOT-BLAST HEATING. 



413 



by a single damper, operated by a thermostat which is so 
adjusted that either the wann-air pipe or the cold-air pipe can 
be opened as desired, but the total supply of air cannot be 
changed by any motion of the damper. 

A complete test of this plant was described by the author 
in Vol. IV. of the " Trans. American Society Heating and 
Ventilating Engineers," from which the following data and 
results are taken : 



































^ 


---- 
































"7IO. 


CXUK 


L. 1 


7^ 






/ 
































\ 




















h- 




i 






















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The heating surface consisted of Inch pipe screwed into 
cast-iron bases or manifolds, arranged in five sections for each 
fan. Each section had four tiers of pipe, and contained for 
the large fan 954 feet of inch pipe and for the small fan 396 
feet. One of these sections was arranged as a tempering coil, 
to warm the air when required before reaching the fan, the 
other four sections were set in the heater coil. The total 
heating surface expressed in lineal feet of one-inch pipe, 4770 
for the large fan and 1980 for the small fan. 

The following table gives the principal dimensions of 
machinery: 



< < tt 

11 n 



414 HEATING AND VENTILATING. 

Large Pan. Small Paiv 

Diameter of wheel, inches 84 44 

Width at centre, inches 36 18 

Diameter of inlet, inches 54 28 

Discharge opening, inches 40X42 22X22 

Diameter engine cylinder, inches 19 - 6 

Length of stroke, inches 8 8 

Heating surface, lineal feet 4770 1980 

heater, lineal feet 3816 1584 

tempering coil, lineal feet 954 396 

Lineal feet of pipe per cubic foot r 12.7 28. 2 

Dimensions of flues from fan : 

Tempered air, inches 40X20 42X10.5 

Warm air, inches 72X28 42X14.25 

Area of flue in square feet: 

Tempered air 5 . 56 3 .06 

Warm air 11.66 4-04 

Velocity of air, feet per minute, by measurement: 

Feb. 13 888. 1186 

Tempered air Feb. 25 1400 1073 

Feb. 13 1000 601 

Warm air Feb. 25 1218 411 

Temperature outside air 32**, Feb. 13, 1897: 

Tempered air 60 63 

Warm air 91.5 ico 

The graphical results of the test on February 25 are shown 
in the two diagrams. 

The results of a test were as follows: 

Large Pan. Small Pan. 

Cubic feet of air per minute 21 ,000 5, 180 

Lineal feet of pipe per cubic foot per minute 4.5 3 . 28 

Pressure in ounces 7/8 1/32 

Revolutions per minute 220 201 

Delivered engine horse-power 5.5 i .01 

Indicated engine horse-power 8.6 1.5 

Steam pressure, pounds 22 22 

Temperature outside air, degrees 34 34 

entering air, degrees 80 136 

of rooms supplied, degrees 70 70 

Heat supplied per minute 4560 5180 

Heat per foot lineal pipe, B.T.U. per minute 0.98 3 . 26 

Pounds of steam condensed per square foot heating surface 

per hour 0.17 0.61 

Cubic feet of space heated 1 21,724 56,732 

Changes of air per hour 10 . i 5.5 

COMPARISON OF RESULTS WITH C.VPACITY AND POWER RULES. 

Cube of diameter of fan in feet 343 49 . 2 

Coefficient for capacity rule 0.3 0.5 

Capacity by rule 22,028 5,250 

Fifth power of diameter in feet 16,807 663 

D'N*-i- 1, 000,000 0.179 0053 

Factor for horse-power by rule 30 20 

Horse-power by rule 5 .37 x.x6 



it 



I 



HOT-BLAST HEATING. 415 

It will be noted that the heating surface for the large ian 
is apparently less efficient than for the small fan; this is 
explamed by the action of the thermostat, which regulated the 
relative amount of hot and tempered air to maintain a uniform 
temperature, and merely indicates that only a portion was 
utilized at the time of the test. It will also be noted that the 
temperature of the air delivered by the small fan was higher 
and the pressure less than was the case with the large fan; this 
in large part was due to the fact that the small fan was only 
run at about two-thirds its rated speed. The necessity for 
ventilation was also less in that portion of the building heated 
by the small fan. The practical operation and use of the 
building has proved that better results would have been pro- 
duced had one fan and beating system been employed instead 
of two, 

200. Tests of Blower Systems of Heating. — The heat given 
off from an indirect radiator over which the air is forced by a 
blower or fan varies with the difference in temperature between 
the steam in the pipe and the surrounding air, with the velocity 
of air, and with the number of rows of pipes over which the 
air passes, A scries of tests were made under supervision 
of the author by blowing air over an indirect heater, con- 
sisting of eight sections, each section containing four rows 
of one-inch pipe and 180.85 square feet of heating surface, 
and arranged so that one or more sections could be employed 
as desired. During each test air was drawn by suction through 
the heater or radiator by an exhaust-fan having a wheel 4 
feet in diameter, driven by an engine. The principal portion 
of the test was made with the fan revolving 400 turns per 
minute, and so as to give a peripheral speed to the tips of the 
fan-whcc-l nt' 5026 feet per minute. The speed of the air 
approaching the heater was for the most part 473 feet per minute, 
but between the coils its speed was about 1250 feet and in the 
discharge-duct 2900 feet per minute; its temperature on enter- 
ing was about 70° Fahr. The tables following give the data 
kms tests expressed In B.T.U. per square 
e difference of temperature between the 



416 



HEATING AND VENTILATING. 



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HOT-BLAST HEATING. 



417 



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418 



HEATING AND VENTILATING. 



steam and the entering air and between the steam and the 
nlean temperature of the air. The tables also give the probable 
B.T.U. per square foot per hour for the entering air at o*^ Fahr., 
this amount being calculated from the results of the test by 
application of the well-known physical law that the heat trans- 
mitted varies almost exactly with the mean difference of tem- 
perature. By dividing this latter quantity by the number of 
heat-units latent in one pound of steam, as shown in a steam- 
table for the required pressure, the weight of steam that would 
be condensed per square foot of heating surface per hour is 
obtained as given in the tables which follow. 

A general table given is computed from the average results 
of the tests by application of well-established physical laws. 

GENERAL TABLE FOR BLOWER SYSTEMS OF HEATING. 



^T « 


Lbs. of Steam Condensed 
per Hr. i>er Sq.ft. H. S. 


B.T.U. per Square Foot 
H. S. per Hour. 


Velocity of Air 1250 Ft. 
per Minute. 


Number 
of Rows 
of Pipes. 


Entering 
Air 70°. 


Entering 
Air 0®. 


Total 
Entering 
Air 70**. 


Per Degree 

Difference 

Steam and 

EnteringAir. 


Increase in 

Temperature 

of Air. 

Deg. Fahr. 


Cu.Pt. Air 

per Sq.Pt, 

H. S. per 

Minute. 


4 
8 

12 

i6 

20 

24 

28 
30 


1-57 
1.32 
I. II 
0.98 
0.90 
0.8s 
0.83 
0.81 


1.67 

1-37 
1. 16 

1.02 

0.93 
0.88 

0.8s 

0.83 


1480 
1240 
1050 
930 
850 
800 
780 

775 


7 
6 

5 
4 
4 
4 
3 
3 


4 

2 

3 

7 

3 


Q 

85 


20 

33 
42 
40 
56 

63 
72 

76.S 


72 

36 

24 
18 

14.4 
12 

10.3 
Q.6 



The temperature of discharge would be increased by driv- 
ing over the radiator smaller quantities of air, and diminished 
by increasing the amount of air, the rise of absolute tempera- 
ture being inversely proportional to the volume. 

It will be noted from the above table that the amount of 
heat given to the air increases very slowly after it has passed 
through or between i6 rows of pipes, and that the economic 
limit of the number of rows of pipes must approximate between 
16 and 24. 

The tests indicate that the total heat transmitted in 
B.T.U. per square foot for a heater with varying rows of 



HOT-BLAST HEATING. 419 

pipes can be expressed very nearly by an equation in which H 
equals the number of heat-units \^x square foot per hour, the 
subscript gives the number of rows of pipes over which the air 
has passed and V equals velocity of air in feet per minute 
between the rows. We shall have for entering air 70° F., 

For one pipe J^i = 250-I- 45 VK. 

For four pipes .^4 = 250-I- 35 VF. 

For eight pipes //g = 250-I- 27 Vp^ 

For twelve pipes i/ii= 250-I- 23 VK. 

For sixteen pipes Hi%^2$o-\- 20 vF. 

For twenty pipes Hio=»25o-|- 17 vK. 

For tewnty-four pipes ^24= 250-I- i6Vk. 

For twenty-eight pipes ^a= 250-f- 15 Vk. 

For thirty pipes A^3o= 250-1-14.7 VF. 

It will be noted in the above equations that when V = Oy H 
in all cases = 250, which approximates the transmission of heat 
in B.T.U. per square foot per hour in still air. The amount 
of heat transmitted for entering air 0° F. will be about 3 per 
cent greater than given by the above equations. 

The heat transmitted per square foot of heating-surface 
per degree difference of temperature of the steam and entering 
air can also be expressed by an equation similar to that given 
for the total heat per square foot per hour. The calculation 
for this case will be rendered easier by using the velocity in 
feet per second, instead of in feet per minute as in the preced- 
ing case. If we denote the velocity of the air over the pipes 
in feet per second by v, the heat transmitted per degree differ- 
ence of temperature per hour by r, with a subscript denoting 
the number of pipes over which the air passes, we shall have* 

For n pipe rn=i-25-\-{22o/sn--n/22o)^Srv, 

For four pipes ri = i. 25+1.35 V p. 

For eight pipes r§ =i.25-f-i.o8Vr. 

For twelve pipes ri2~i.2$-\- .91 vi. 

For sixteen pipes ri6= 1.25-h .75 v p. 

For twenty pipes r^o- 1.25-f- .67 V p. 

For twenty-four pipes r..4= 1.25-I- .60V p. 

For twenty-eight pipes ra= 1.25+ .58 V p. 

For thirty pipes r^= 1.25-I- .57 v v. 



420 



HEATING AND VENTILATING. 



It will be noted in the above equations that for »=o, /■= 1.35 
in all cases. 

In many cases the entering air ordinarily passes first 
through a heater of sufficient extent to warm it to 70'* F, in 
zero weather, which is termed a tempering coU; from thence 







it passes either through the main radiator or heater or directly 
to the room, as may be necessary to maintain the proper 
temperature without changing the volume of air supplied. 
201. Charts for Vento Heaters, from paper by L. C. Soule, 
before the A. S. H. & V. E., 1913. 



HOT-BLAST HEATING. 



"*■ 














































































































































































































/ 


























































/ 




































{ 














































































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/ 




^ 




















^ 
































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y 


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^ 




























/ 










,^ 


















/ 


























































































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- 
























































iM 


^^^ 


A-fl^ 


■wo.^ 


■jbote' 


■i^ 


^ 


^«uft! 


ti- 


f 







Fig. 371. — Chart Showing Friction Losses. Vento. 




FlC. 171. — Plan and Elevation Showing Location of Testing Apparatus. 

202. Table for Wrought-iron Pipe Heaters, by Frank L. 
Busey, before the A. S. H. & V. E., 1912: 



HEATING AND VENTILATING. 





d 

1 


1 
1 


1 


Ni 


11111355 


pn-ssH 




« 


- » » »<J CT-O - 


.9ac>-9-° 




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;;sEss=; 


1 


1 


Nt 


lis.-BH 


lisHlfl 


ft 


n 




««««*,-«„ 




*S»5S|^^ 


rsKSss^s 


3 

B 
Q 

1 


1 


m 


HISsSH 


1-3115 = 


n 


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=5S-S=S5 


i 1 

3 ' 


1 






JjisS-H 


3 


& 
1 
.E 

•3 

> 


n 


=S55|2S5. 


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m 


1 




ir=Hi=-: 


sHsSsss 


II 




-i-^atoosn 


s 


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Nt 


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u 


II 


::S£g^S3| 


SS£?=5SS 


1 


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11 


oo- = «=-»- 


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°8 

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HOT-BLAST HEATING. 



UiBin 


SBUB 


IHSIIil 


IHHsSI 








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sassKS^? 


"=•= = = = 


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jssissss 


ssiss^^s 


SSSSSS^i 


^ssiaiy 


BUBB 


5SIIH3S 


tsslBl- 


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HIsEsI 


sIk^HS^ 


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sllHlsa 




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B3?S2?as 


ss:s;s5; 


5SS 32353 


SS3^|S|3 


Sslsllss 


Sarsl-SI 


sslSHs; 


ssssHis'S 


:iS5g|:S58 


^si^s^^s 


-i-- = o-.««-> 


a»o--o«,~ 


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5 S 251 ESS 


5ss5IS53 


IsS;H55 


ssSsIsj: 


1Hj«H«5 






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424 HEATING AND VENTILATING. 

203. Carrier's Theory of Convection with Forced C^reolatioiL* 

From experimental investigation they conclude that the 
exterior of the conducting wall is covered with a surface film 
into which heat passes directly from the conducting wall, and 
whose resistance to the passage of heat is independent of the 
velocity of the convecting medium; but it is a direct function 
of the density and specific heat of that medium. 

The total resistance of the surface film of the steam, of the 
conducting wall, and of the surface film of the conducting 
medium, may therefore be represented by a constant U, which 
is independent of the temperature difference between the steam 
and the convecting medium, and of the velocity of the latter. 

Exp)erimental investigation also indicates that heat is trans- 
ferred from the surface film to the main body of the convecting 
medium, that is to the air, entirely by displacement. Particles 
of air in the surface film are displaced by impact, due to the 
velocity of the air over the surface, and are thus mixed with 
the main body of the air. This displacement may be shown 
to be in direct proportion to the velocity. The rate of heat trans- 
fer to the air is therefore directly proportional to the product of 
the velocity and temperature difference between the film and air. 

Let 6t represent the steam temperature, Cp the specific heat 
of the air, and 5 is a constant to be determined. 

Let Wo and Vq be the corresponding densities and velocities 
of the air at an absolute base temperature ^0 and let $ be the 
absolute temperature of the air corresponding to W and V 
then 

Let K be the rate of transmission in B.T.U. per square foot 

per hour per degree difference in temperature between the 

steam and air. Then 

I 



K = 



Dj B 

CpWoVo 



* From paper by Willis H. Carrier and Frank L. Buscy before the A. S. M. E^ 
December, 191 1. 



HOT-BLAST HEATING. 425 

Let Ht be the total heat transferred per hour from a sur- 
face S. 

H,^K{e,-e)S 

G= weight of air per hour passing over the surface S. 

Ks.cfi i«g.(«^;) 

where 

A = clear area through heater having surface 5; 
F = velocity in ft. per min. through clear area; 
W^=density of air in lb. per cu.ft. 

G = 6oAWV = 6oAWoVo 
Hence 

KS 



-•(i^)= 



6oC,AWoVo 
Changing this to common logarithms 

KS 



^^«C^;)=(r 



3026x6o)CVlIf'oKo 
K = ' 



CpWoVo 



'-(|^)= 



5 



(2.3026 X 6o)/lCyFo(/?Fo + ~- ) 



(2.3026X60^ {RC/2+BA) 

where ^= cu.ft. of air per minute at standard temperature. 
Will also reduce to 

log(«-li')=^^ 
^ \ft-«2/ mV-\-n 

S 

/= -j; n is a constant, and m is substantially a constant except 

A 

as varied by change in the absolute temperature of the surface 
film. 



HEATING AND VENTILATING. 



1- 

r 




III = iJf§|8s 




!!!!!!!! ^!? 




§>||llf!!?ff 1 


-ini"1V ""W 


iiiiiiiiill 1 


1 


■AlpopA 


ssiuiyiii 




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1 


mild ■p'"»lS 

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msium 


1 
i 

>-< 

1 

1 


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iiiuir^^i 


«,«o t-COOD OO 


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3SSs:ms^l ; 


'lis 


sS^itsflsB 


--""-' "iZZ 


5 
1 


j^i«!5^»D 


isiU'ASVtl 




35?3t55?3ll ? 




-111* J. rail J 


Iilillillil J 




1 





CHAPTER XVI. 
HEATING WITH ELECTRICITY. 

204. Equivalents of Electrical and Heat Energy. — Electrical 
energy can all be transformed into heat, and as there are certain 
advantages pertaining to its ready distribution, it may come into 
more extended use for heating, especially where the cost is not 
of prime importance. Electricity is usually sold on the basis 
of 1000 watt-hours called a kilowatt hour, the watts being the 
product obtained by multiplying the amount of current in 
amperes by the pressure in volts; on this basis one kilowatt 
hour is the equivalent of 3410 heat-units. Either direct or 
alternating current may be used as they have equal heating 
value per kilowatt. The voltage should not be higher than 
that ordinarily used for incandescent lighting. 

205. Expense of Heating by Electricity. — ^The expense of 
electric heating must in every case be very great, unless the 
electricity can be supplied at an exceedingly low price. Much 
data exists regarding the cost of electrical energy when it is 
obtained from steam-power. Estimated* on the basis of 
present practice, the average transformation into electricity 
does not account for more than 4 per cent of the energy in 
the fuel which i^ burned in the furnace; although under best 

*The mechanical energy in one horse-power is equivalent to 0.707 B.T.U. 
per second or 2545 per hour. One pound of pure carbon will give of! 14,500 
heat-units by combustion, which if all utilized would produce 5.7 horse-power 
for one hour, in which case one horse-power could be produced by the combus- 
tion of 0.175 lb. of carbon. The best authenticated actual performance is one 
horse-power for 1.2 lb., corresponding to 14.6 per cent efficiency. The usual 
consumption is not less than 4 to 6 pounds per indicated horse-power, or from 
3 to 5 times the above. A kilawait is very nearly 1} horse-power, but because 
of friction and other losses requires an engine of T.5 indicated horse-power. 

427 



428 HEATING AND VENTILATING. 

conditions 15 per cent has been realized, it would not be safe 
to assume that in conunercial enterprises more than 5 per 
cent could be transformed into electrical energy. In transmit- 
ting this to a point where it could be applied losses will take 
place amounting to from 10 to 20 per cent, so that the amount 
of electrical energy which can be usefully applied for heat- 
ing would probably not average over 4 per cent of that in the 
fuel. In heating with steam or hot water or hot air the average 
amount utilized will probably be about 60 per cent, so that the 
expense of electrical heating is approximately as much greater 
than that of heating with coal as 60 is greater than 4, or about 
15 times. If the electrical current can be furnished by water- 
power which otherwise would not be usefully applied, these 
figures can be very much reduced. The above figures, are made 
on the basis of fuel cost of the electrical current, and do not 
provide for operating, profit, interest, etc., which aggregate many 
times that of the fuel. With coal at $3.30 per ton this cost 
on above basis is about .97 cent per thousand watt-hours. 
The lowest commercial price quoted, known to the writer, 
for the electric current was 3 cents per thousand watt-hours; 
the ordinary price for lighting current varies from 10 to 20 cents. 
It may be said that for lighting purposes 10 cents per thousand 
watt-hours is considered approximately the equivalent of gas 
at $1.25 per thousand cubic feet. 

It may be a matter of some interest to consider the method 
of computation employed for some of these quantities. The 
ordinary steam-engine requires about 4 pounds of coal for each 
horse-power developed; on account of friction and other losses 
about 1.5 horse-power are required per kilowatt, or in other 
words 6 pounds of coal are required for each thousand watts 
of electrical energy. In the very best plants where the output 
is large and steady this amount is frequently reduced 20 to 30 
per cent from the above figures in cost. The cost of 6 ix)unds 
of coal at $3.33 per ton is one cent. To this we must add 
transmission loss about 10 per cent, attendence and interest 20 
per cent, making the actual cost per kilowatt 1.3 cents per 
hour. As one pound of coal represents from 13,000 to 15,000 



HEATING WITH ELECTRICITY. 



429 



heat-units, depending upon its quality, and one kilowatt-hour 
is equivalent to 3415 heat-units, if there were no loss whatever 
in connection with transformation of heat into electricity, one 
pound of coal should produce 4 to 5 kilowatts per hour of 
electrical energy. This discussion is sufficient to show that at 
cost prices electrical heating obtained from coal will amount 
under ordinary conditions to 15 to 20 times that of heating 
with steam or hot water, and at commercial prices which are 
likely to be charged for current its cost will be from 2 to 10 
times this amount. 

The following table gives the cost of a given amount of heat, 
if obtained from the electric current, furnished at different 
prices. Thus 30,000 heat-units if obtained from electric current 
furnished at 8 cents per kilowatt hour would cost 70.28 cents 
per hour. The amount of heat needed for various buildings 
can be determined by methods stated in Chapter III. 

COST OF HEAT OBTAIXED FROM ELECTRICITY. 





Cost per kilowatt hour, cents. 


Heat- 






















units. 


I 


2 


3 


4 


s 


6 


7 


8 


9 


10 


B.T.U. 
























Cost of heat obtaine 


d, cents. 




10,000 


2 93 


5.86 


8.78 


II. 71 


14.64 


17.57 


20.50 


23.42 


26.35 


29.28 


20,000 


5. 85 


11.68 


1757 


23.42 


29.28 


35.13 40.99I 46.84 


52.70 


58.56 


30,000 


8.78 


1757 


26.35 


35-14 


43 92 


52.70 61.49 


70.28 


79.06 


87.84 


40,000 


II. 71 


22.42 


35 14 


46.84 


58.56 


70.28 81.98 


93.68 


105.40 


117. 12 


50,000 


14.64 


29.28 


43 92 


58.56 


73.20 


87.84 I02.48lli7.i2 


131.86 


146.40 


60,000 


1757 


35 14 


52.70 


70.28 


87.84 


105.40 


122.98:140.56 


158.12 


175.68 


70,000 


20.50 


40.99 


61.49 


81.98 


102.48 


122.98 


143.47 


163.96 


184.46 


204.96 


80,000 


23.42 


46.84 


70.28 


03.68 


117. 12 


140.56 


163.97 


187.36 


210.80 


234 24 


90,000 


26.35 


52.70 


79.06 


105.42 


131.76 


158.10 


184.46 


210.84 


237.17 


263.52 


100,000 


29.28 


58.56 


87.84 


117. 12 


146.40 


175.68 


204 . 96 


234 . 24 


263.52 


292.80 



Note. — 10,000 heat-units is equal to two-thirds the heat contained in one 
pound of the best coal, and is very near the average amount that can be realized 
per pound in steam or hot-water heating, hence the table can also be considered 
as showing the relative price of electricity and coal for the same amount of heat- 
ing. For instance, if 5 cents per kilowatt hour is charged for electric current, the 
expense would be the same as that of good coal at 14.64 cents per pound, which 
is at rate of $392.80 per ton. 



430 HEATING AND VENTILATING. 

There are some conditions where the cost is not of moment 
and where other advantages are such as to make its use desir- 
able. In such cases electricity will be extensively used for 
heating. 

For the purposes of cooking it will be found in many cases 
that electrical heat, despite its great first cost, is more econom- 
ical than that obtained directly from coal. This is due to the 
fact that of the total amount of heat, which is given off from 
the fuel burned in a cook stove very little, perhaps less than 
one per cent, is applied usefully in cooking; the principal pwirt 
is radiated into the room and diffused, being of no use what- 
ever for cooking, while the heat from the electric current can 
be utilized with scarcely any loss. 

~ 2o6. Formulae and General Considerations. — The following 
formulae express the fundamental conditions relating to the 
transformation of the electric current into heat: 

^=1 W 

W=^CE==C^R (2) 

R=— (3) 

H=o,24(yR (4) 

//i = . 0000000956'^/? (5) 

A2 = 3.4iS^^' = 34i5C^^ = 3-4i5C£. ... (6) 

In which the symbols represent the following quantities: £, 
electromotive force in volts; C, intensity of current in amperes; 
R, resistance of conductor in ohms; /, the length in metres; 
w, the area of cross-section in square centimetres; k, coefficient 
of specific resistance; H", kilowatts; H, the heat in minor 
calories, and hi in B.T.U. per second, 7/2 the heat in B.T.U. per 
hour. 

The amount of heat given off per hour is given in equation 
(6), and is seen to be dependent upon both the resistance and 



HEATING WITH ELECTRICITY. 



431 



the current, and apparently would be increased by increase in 
either of these quantities. The effect, however, oi increasing 
the resistance as seen by equation (i) will be to reduce the 
amount of current flowing, so that the total heat supplied 
would be reduced by this change. On the other hand, if there 
were no resistance no heat would be given off, for to make 
R=o in equation (6) would result in making /i3 = o. From 
these condderations it is seen that in order to obtain the maxi- 
mum amount of heat, the resistance must have a certain mean 
value dependent upon the character of material used for the 
conductor in the heater, its length and diameter. 




Fig. 373. — DiaKtam of Electric Heating. 



The principle of electric heating is much the same as that 
involved in the non-gravity return system of steam-heating. 
In that system the pressure on the main steam-pipes is essen- 
tially that at the boiler, that on the return is much less, the 
reduction of pressure occurring in the passage of the steam 
through the radiators; the water of condensation is received 
into a tank and returned to the boiler by a steam-pump. In a 
system of electric heating the main wires must be sufficiently 
large to prevent a sensible reduction in vollage or pressure 
between the dynamo and the heater, so that the pressure in 
them shall be substantially that in the dynamo. The pressure 



432 



HEATING AND VENTILATING. 



or voltage in the main return wire is also constant but very low, 
and the dynamo has an office similar to that of the steam- 
pump in the system described, viz., that of raising the pressure 




Fto. 174'— Office or House Bcftter. 

of the return current up to that in the main. The power 
which drives the d>"namo can be considered s>-non>'mous with 
the boiler in the other case. All the current which passes from 
the main to the return current must flow through the beater, 



HEATING WITH ELECTRICITY. 433 

and in so doing its pressure or voltage falls from that of the 
main to that of the return. 

Thus in the diagram, a generator is located at D, from which 
main and return wires are run, much as in the two-pipe system 
of heating, and these are so proportioned as to carry the 
required current without sensible drop or loss of pressure. 
Between these wires are placed the various beaters; these 
are arranged so that when electric connection is made, they 
draw current from the main and discharge into the return wire. 



\ 

3 




u. 



Fig. J7S.— Twin Glower Electric Radiator. 



CormectioQS which are made and broken by switches take 
the place of valves in steam-heating, no current flowing when 
the switches are open. 

The heating e£fect is proportional to the current flowing, 
and this in turn is affected by the length, cross-section, and 
relative resistance of the material in the heater. The resist- 
ance is generally proportioned such as to maintain a constant 
temperature with the electromotive force available, and the 
amount of heat is regulated by increasing the number of con- 
ductors in the heater. 



434 



HEATISU AND.\-ENT1LAT1NG. 



207. Constructioii of Electrical Heaters. — Various forms 
of beaters have been employed. Some of the simplest consist 
merely of coUs or loops of iron wire arranged in parallel rows 
so that the current can be passed through as many wires as 




76. — Car Heater ot Consolidated C 



are needed to provide the heat required. In other forms 1 
these beaters the heating material has been surrounded witf 
fire-clay, enamel, or some relatively poor conductor, and 
other cases the material itself has been such as to give consid- 




erable resistance to the current. It is generally ( 
the most satisfactory results are obtained with electrical as with 
other heaters by regulating the resistance, by change of length 
and cross-section of the conductor, to such an extent as to keep 



HEATING WITH ELECTRICITY. 436 

the heating coils at a moderately low temperature. Some of 
the various forms which have been used are shown in the cuts. 
The electrical heating surface is made in the latter by a coil 
of wire wound spirally about an incombustible day core. The 
casing is like that for an ordinary stove, and is built so that air 
will draw in at the bottom and pass out at the top. 

The electrical heaters at the present time are used almost 
exclusively in heating electrical cars, where current is available 
and room is of considerable value. These heaters are generally 
located in an inconspicuous place beneath the seats, their gen- 
eral form being shown by the illustrations. 

208. Connections for Electrical Heaters. — ^The method of 
wiring for electrical heaters must be essentially the same as for 
lights which require the same amount of current. The details 
of this work pertain rather to the province of the electrician 
than to that of the steam-fitter or mechanic usually employed 
for installing heating apparatus. These wires must be run in 
accordance with the underwriters' specifications, so as not, 
under any conditions, to endanger the safety of the building 
from fire. 



CHAPTER XVn. 



TEMPER.\TURE REGULATORS. 



209. General RemaiiEs. — A temperature regulator is an 
automatic dewe which will open or dose, as required to pro- 
duce a uniform temperature, the \'alves which control the 
supply of heat to the various rooms. Although these regula- 
tors are often constructed so as to operate the damp>ers of the 
heater, they differ from damper-regulators for steam-boilers, 
by the fact that the latter are unaffected by the temperature 
of the surrounding air, although acting to maintain a uniform 
pressure and temperature within the boiler, while the former 
are put in operation by changes of temperature in the rooms 
heated. 

The temperature regulator, in general, consists of three 
parts, as follows: First, a thermostat which is so constructed 
that some of its parts will move because of change of tempera- 
ture in the surrounding air, the motion so produced being used 
either directly or indirectly to open dampers or valves, and 
thus to c(mtrol the supply of heat. Second, means of trans- 
mitting and often of multiplying the slight motion of the parts 
of the thermostat produced by change of temperature in the 
T(X)m, to the valves or dampers controlling the supply of heat. 
Third, a motor or mechanism for opening the valves or damp)ers, 
which may or may not be independent from the thermostat. 

In some systems the thermostat is directly connected to 
the valves or dampers, and no independent motor or mechanism 
is employed; in this case the power which is used to open or 
clo.se the valves regulating the heat-supply is generated within 
the thermostat, and is obtained either from the expansion or 
contraction or metallic bodies, or by the change in pressure 
caused by the vaporizing of some liquid which boils at a low 

436 



TEMPERATURE REGULATORS. 



437 



temperature. The force generated by slight changes in tem- 
perature is comparatively feeble, and the motion produced is 
generally very slight, so that when no auxiliary motor is 
employed it is necessary to have the regulating valves constructed 
so as to move very easily and not be liable to stick or get out of 
order. In most systems, however, a motor operated by clock- 
work, water, electricity or compressed air is employed, and the 
thermostat is required simply to furnish power sufficient to 
start or stop this motor. The limits of this work do not permit 
an extended historical sketch of many of the forms which have 
been tried. The reader is referred to Knight's Mechanical 
Dictionary, article " Thermostats," and to Peclet's " Trait6 
du la Chaleur," Vol. II, for a description of many of the early 
forms used. Those which are in use may be classified either 
according to the general character of the thermostat or the 
construction of the motor employed to operate the heat- 
regulating valves as follows: 



Thermostats 



Moved by 
expansion or 
contraction. 

Moved by 
change of 
pressure. 



f No auxiliary f Expansion or 

' contraction. 



Temperature 
Regulators 



motor 



I Pressure. 



" Clockwork. 
Motor ' Water. 

, Compressed air. 

Electrical ( Magnets. 
I Motors. 

210. Regulators Acting by Change of Pressure. — ^A change 
of temperature acting on any liquid or gaseous body causes 
a change in volume, which in some instances has been utilized 
to move the heat-regulating valves so as to maintain a con- 
stant temperature. Fig. 278 represents a regulator in which 
the expansion or contraction of a body of confined air is utilized 
to control the motion of the dampers to a hot-water heater. 

It consists of a vessel containing in its lower portion a 
jacketed chamber connected to the hot-water heater at points 
of different elevation so as to secure a circulation from the 
heater through the lower portion or jacket of the vessel from 
2 to 3. Above this is a second chamber which is covered on 



HEATING AND VENTILATING. 



top with a rubber diaphragm, and which contains a funnel- 
shaped corrugated brass cup. The opening to the cup is ui 
the lower portion of the chamber, the top and larger surface 
resting against the rubber diaphragm. Enough water at 
atmospheric pressure or alcohol is poured into the upper cham- 
ber through the opening marked i to seal the orifice in the 
inverted cup and confine the air it contains. The regulator 
acts as follows: The warm water from the heater mo^'ing 
through the lower chamber communicates heat to the water 
or alcohol in the upper chamber, which in turn warms the air 
in the inverted cup, causing it to expand. This moves the 



n 



K 




Fic. 378. — Lawlcr Hot-wj 



rubber diaphragm and connected levers leading to the dampcfs 
substantially as in the damper-regulator for steam-heaters, 
already described. 

211. The Powers Regulator for hot-water heaters (see Fig. 
279) is somewhat similar in construction to the one described, 
but acts on a different principle. A liquid which will vaporize 
at a lower temperature than that of the water in the heater is 
placed in the vessel communicating with the diaphragm, in 
which case considerable pressure is generated before the water 
in the heater reaches the boilmg-point. As the water in the 
heater is usually under a pressure of 5 to 10 pounds per square 
inch, its boiling temperature is from 225 to 240 degrees, water 
of atmospheric pressure which boils at 212° can be used in the 



TEMPERATURE REGULATORS. 



439 



closed vessel, and will generate considerable pressure before 
that in the heater boils. 

The method of construction is shown at the right, in Fig. 
279, as applied to a hot-water heater. The diaphragm employed 
consists of two layers of elastic material with compartments 
between and beneath; the lower one is connected to the cham- 
ber A, which is filled with water at atmospheric pressure and is 
surrounded by the hot water flowing from the heater. The 
water in chamber .-1, being under less pressure, will boil before 
that in the heater, and will produce sufficient pressure to move the 
diaphragm and levers so as to close the dampers, before the 
water in the heater reaches the boiling-point. The compart- 




^^K Bi a 



ment between the two diaphragms, //, is in communication 
with a vessel D, which in turn is connected by a closed pipe E 
with a thermostat, which may be placed at any point in the 
house and so arranged that if the temperature becomes too high 
in that room, the dampers of the heater will be closed. With 
this apparatus the dampers are closed either by excessive tem- 
perature of water at the heater or too great a heat in any room. 
The intermediate compartment Is only required when the dam- 
pers are to be operated by change of temperature in the rooms. 

The thermostat employed in this apparatus consists of a 
vessel 2, Fig. 279, separated into two chambers by a diaphragm; 
one of these chambers, B, is filled with a liquid which will boil 
at a temperature below that at which the room is to be main- 

led; the other chamber, A, is filled with a liquid which 



440 



HEATING AND VENTILATISG. 



does not boU, and is connected by a tube to a diaphragm dam- 
[ler-regulator which moves the dampers through the medium 
of a series of levers. 

Fig. 279, 2, shows a transverse section of a thermostat, i 
an elevation with parts broken away, and Fig. 2S0 an ele- 
vation with attached thermometer. The vapor of the liquid 
in the chamber B produces considerable pressure at the normal 
temperature of the room, and a slight increase of heat crowds 
the diaphragm over and forces the liquid in the chamber A 
outward through a connect- 
ing tube which leads to the 
damper- regulator, one form 
(if which has been described. 
The damper-regulator as 
applied to a steam-heater is 
provided with a single rub- 
bur diaphragm with the parts 
arranged as shown in the 
sectional view Fig. 2S1. In 
this case the liquid pressure 
is applied above the dia- 
phragm, its weight being 
counterbalanced by springs and weights, attached to the levers. 
The liquid used in the thermostat may be any which has a 
boiling temperature somewhat below that at which the roo^^ 
is to be kept. Many 
liquids are known 
which fulfil this con- 
dition, of which we 
may mention ethclint'. 
bromine, various pc 
troleum distillates, al- 
cohol, anhydrous am- 
monia, SO3. and liquid 
carbonic acid. The 

liquids employed in the Powers thermostat are said I 
pressures as follows at the given temperatures: 




Fig. i8o. — Elcvution of Thcrmoslat. 




Fig. j8 I .—Diaphragm tlamper-rcgulaur. 



TEMPERATURE REGULATORS. 441 



At 60° I pound to the square inch. 

" 65° 2| " 

" 70° 4 " 

75 52 

'' 80° 7 '' 

'' 90° 10 *' 

'' 100° 13 '' 

212. Regulators Operated by Direct Expansion. — Metals of 
various kinds expand when heated and contract when cooled, 
and this fact has often been utilized in the construction of 
temperature regulators. 

A single bar of metal expands so small an amount that it is 
of little value for this purpose unless very long, or unless its 
expansion is multiplied by a series of levers. Several forms 
have been used, of which may be mentioned: a bent rod with 
its ends confined so that expansion tends to change its curva- 
ture; a series of bent rods of oval form resting on each other 
with the ends confined between two fixed bars; two metallic 
bars having different rates of expansion arranged parallel and 
the variation in length multiplied by a series of connecting 
levers an amount sufficient to be available in moving dampers; 
two strips of metal of different kinds bent into the form of an 
arc and fastened together so as to form a curved bar, with 
the metal which expands at the greater rate on the inside, so 
that expansion tends to straighten it when heated; the differ- 
ence in expansion between an iron rod which is not heated 
and the flow-pipe of a hot-water heater multiplied by means 
of a series of levers. The constructions described above have 
all been tried for the purpose of moving the dampers of heaters 
or for opening and closing valves. In general, however, they 
have not proved satisfactory, because of the slight motion 
caused by expansion, and the uncertainty of operation obtained 
with multiplying devices. 

Temperature regulators with time clock attachments are 
made by attaching a small alarm clock which will shift the 
adjustment of the thermostat back to the normal of 70 degrees, 
at any predetermined hour, thus allowing the house to be kept 



442 HEATING AND VENTILATING. 

at a lower temperature during the night by shifting the adjust- 
ment of the thermostat each night. They are more commonly 
used with the type of electrical thermostats "in which the 
metal expansive element makes one electrical contact to raise 
the temperature and another in the opposite direction to 
lower the temperature. The electrical contact is made by 
actuating a magnet or a motor which in turn moves the 
dampers, either directly or by means of some clockwork 
mechanism. 

The direct expansion of a liquid or of a gas in a confined 
vessel has also been utilized to move a diaphragm or piston 
which is connected by levers to the dampers of heaters, in 
a manner similar to that described in the preceding article. 
The writer at one time constructed a regulator for a hot-water 
system in which the expansion of water in a closed vessel sur- 
roimding the return-pipe was employed to operate a damper- 
regulator similar to those used in steam-heating. Pfclet 
describes regulators in which the expansion of air was employed 
to move a piston connected by cords and pulleys to the dampers. 

213. Relative Rates of Expansion. — By vaporizing a liquid 
an expansion of many thousand times that obtained by simply 
heating that liquid is obtained. The following example is com- 
puted from the steam tables to show the enormous increase 
in the expansion obtained by the vaporizing of a liquid over 
that due to the direct expansion only of the same liquid, 
which is water in this case. One pound of water expands from 
0.01663 cubic foot to 0.01670 cubic foot when heated from 200® 
to 210° F., or 0.000007 cubic foot increase in volume per one 
degree rise in temperature. Water at 212 degrees when heated 
and turned into steam at 212 degrees expands from 0.01671 
cubic foot to 2.167 cubic feet, or 2.15029 cubic feet for one 
degree. The relative rates of expansion equal 2.15029 -^ 0.000007 
or 307,000. Thus water expands about three hundred thousand 
times more by being vaporized than by being heated one degree. 
Other liquids have similiar characteristics. 

214. Regulators Operated with Motor — General Types. — ^The 
regulators which have been described in the preceding articles 



TEMPERATURE REGULATORS. 443 

operate the regulating valves with a feeble force acting through 
a considerable range, or with a considerable force acting through 
a short distance. They are consequently liable to be rendered 
inoperative by any accident to the levers or connecting tubes, 
or by any cause which renders the valves difficult to operate. 
To overcome such difficulties several systems have been devised 
in which the power for operating the dampers should be obtained 
from an independent source, and in which the work required 
of the thermostat would be simply that of starting and stopping 
an auxiliary motor. In the first systems of this kind the motor 
employed was a system of clockwork which had to be woimd 
at stated intervals in order to supply the force required for 
moving the dampers. In recent systems electricity, water, or 
compressed air is employed to generate the power required, 
and in some instances regulators are arranged to operate not 
only the valves which supply heat to the rooms, but also the 
various dampers for supplying hot or cold air in the ventilating 
system. 

In all of the early forms of this kind of regulator the 
thermostat consisted of a tube of mercury or a curved strip, 
made of two metals of different kinds soldered together and 
arranged so that a given change of temperature would produce 
sufficient motion to make or break electric contact. A current 
was obtained from a battery, and connecting wires led to the 
motor and to the various terminals. When electric contact was 
made at a position corresponding to the highest temperature, the 
current would flow in a certain direction and cause a magnet 
to release a pawl which would start a motor revolving in the 
proper direction for closing the valves. When the temperature 
fell below a certain point, the thermostat would make electric 
connections so that the current would flow in the opposite 
direction and cause the motor to reverse its motion, thus open- 
ing the valve. If the motor was operated by water, the electric 
current would open and close a valve in the supply-pipe; if 
the motor was operated by electricity, the current from the 
battery would move a switch on the wires leading to the 
motor. 



444 



HEATIiVG AND VENTILATING. 



The valves for regulating the heat-supply are made in a 
great variety of ways. Dampers for regulating the flow in 
chimneys or flues are generally plain disks, balanced and mounted 
on a pivot, so that they may be turned ver^' easily; globe- 
or gate-valves are usually employed in steam-pipes and must, 
to give satisfactory service, either be closed tight or opened 
wide. A system in which steam-valves are operated requires 
much more power than one in which dampers only are moved- 
Many systems of heat-regulation employing motors arc 
in use and are doubtless worthy an extended notice, but space 
will only permit a short description of the one in most extensive 
use in the larger buildings of this country, namely, the John- 
son system of temperature regulation, 

215. Pneumatic Motor System. — In the Johnson system 
of heat- regulation the motive 
force for opening or closing the 
valves which regulate the heat- 
supply is obtained from com- 
pressed air which is stored in 
a reservoir by the action of an 
automatic motor. The ther- 
mostat acts with change of 
temperature to turn off or on 
the supply of compressed air. 
UTien the air-pressure is on, 
the valves supplying heat arc 
closed; when off, they are opened 
by strong springs. The detailed 
construction of the parts are as 
follows : 

The compressed air is sup- 
plied by an automatic air-com- 
pressor which is operated in 
small plants by water-pressure 
and acts only when the sup- 
ply of compressed air l 
The external form of I 




— Exlemol View of Smiill 
A ir-com pressor. 



below the limit of pressure 



lir has faUc^^ 
of the^^H 



TEMPERATURE REGULATORS. 445 

compressor is shown in Fig. 2S2. It consists of a vessel divided 

into two chambers by a diaphragm; one chamber is connected 
to the water-supply, the other to the atmosphere. The water 
entering on one side crowds the diaphragm over until a certain 
position is reached when the supply-valve is closed and a dis- 
charge-valve is opened, after which the diaphragm returns to 
its original place. The motion of the diaphragm backward and 





Fig. ?8j.— Seclbnal View of 
Diaphragm- valve. 

forward serves to draw in and discharge air from the other 
chamber m a manner similar to the operation of a piston-pump, 
valves being provided on both inlet- and discharge-pipes. 
When the air-pressure reaches a certain amount, the pump 
ceases its operation. 

An air-pipe leads from the air-compressor to the thermostat, 
and another from the thermostat to the diaphragms in con- 
ation with valves or dampers. The action of the thermo- 
(at, as already explained, is simply to operate a minute valve 



446 



HEATING AND VENTILATING. 



for supplying or wasting, as necessary, compressed air in the 
pipe leading from the thermostat to the diaphragm-valves. 

Fig. 283 is a sectional view of the diaphragm-vahre, the 
compressed air being admitted above the valve and acting 
merely to close it. It can also be closed if necessary by hand. 
The compressed air can also be made to operate dampers of 
which various styles are used, and these may be placed in ven- 
tilating flues, hot-air pipes, or smoke-flues, and so arrcinged as 
to admit either warm or cold air alternately to a room, as may 
be required to maintain a uniform temperature. Fig. 2S4 
shows a damper for two round Sues, one for cold air, the other 




85.— Double Damper In Brick Duct. 



for hot, connected to a diaphragm and arranged so that when 
one is open the other will be closed. 

This system of heat-regulation has been brought to a very 
high degree of perfection, and if sufficieat heat is supplied the 
temperature of a room is maintained with certainty within 
one degree of any required point. Farther than that, the 
system is so arranged that after all the rooms of the house reach 
the desired temperature the heat-regulator then acts to close 
the furnace-dampers. The apparatus is in extensive use for 
regulating temperature in the hot-blast sj-stem of heating. 
Fig. 285 shows the method ad<^ted of appl>-tng a damper- 
r^ulatoc to • sUck for indirect heating which is so arranged 
laim or cool air as necessar>- to maintain 



TEMPERATURE REGULATORS. 



447 



216, Construction of Pneum&tic Thennostat — The following 
diagram and explanation will render the principle of action of 
the pneumatic thennostat as employed In the Johnson system 
of heat regulation intelligible. 

Fig. 286 shows to different scales the reservoir for com- 
pressed air, a diagram of the thermostat and of a diaphragm 
for operating dampers. The thennostat is drawn relatively to 



^ 




THERMOSTAT 

b 
Fig. 2S6. — DiagTBm lUustratins tbe Pneumaitic Thennostat. 



a very large scale. The temperature regulator as a frhole 
counts first of an air compressor, as shown in Fig. 282, or one 
of similar construction, and so ananged as to maintain a con- 
stant pressure in air reservoir J? or in the pipes of the building. 
The principle of operation of the thermostat is illustrated 
by the diagram, although the details of construction of the 
actual instrument are quite different. Compressed air from the 
reservoir or air-pump passes through the pipe A to the cham- 
ber B, thence, if the double valve ab is open, it will pass out 



448 HEATING AND VENTILATING. 

through the pipe C to the chamber V above the diaphragm. 
Its pressure then causes the end X' of the lever X'X to move 
downward. This lever is connected to the damper in such a 
manner as to close oflf the supply of heat when in the lowest 
position. If the room becomes too cold, mechanism to be 
hereafter described moves the valve ab into such a position as 
to close the communication to the compressed air in the cham- 
ber B and open communication with the atmosphere at b. 
This permits the air to escape from the chamber 7, through the 
pipe C and opening J, into the air, the diaphragm in the lower 
part of the chamber V being moved upward by a spring or 
weight not shown in the sketch. Thus it is seen that by mov- 
ing the double valve ab the chamber V is put in communication 
with the compressed air and the damper moved to close oflF the 
heat, or with the outside air, in which case the pressure in the 
chamber V is lessened and the damper is moved by action of a 
weight or a spring so as to admit the warm air. 

The mechanism for moving the valve ab consists of a 
thermostat T, which may be made of any two materials having 
a diflferent rate of expansion, as rubber and brass, zinc and 
brass, etc. Connected to the thermostatic strip is a small 
valve K, so adjusted that when the room is too warm the valve 
will be opened and when too cold it will be closed by the expan- 
sion and contraction of the thermostatic strip. Suppose 
the room too warm and the valve K open, air then flows through 
the chamber 5, through the filtering cotton in the lower part 
of 5', thence through the small tube d and the valve K to the 
air. The small tube d connects with an expansible cham- 
ber D and opens back of a small diaphragm. When the valve 
K is open the spring 5 forces the diaphragm into the con- 
tracted or collapsed position, causing the lever GF to move 
the valve ab so as to put the chamber B in communication with 
chamber V and permit the air-pressure to close the damper 
connected to the lever X'X. If, however, the room becomes 
too cold, the thermostat T moves so as to close the valve K; 
this stops the escape of air from the pipe d and causes suflident 
pressure to accumulate under the diaphragm at D to move the 



TEMPERATURE REGULATORS. 



449 



lever FG, so as to move ab to the left, thus cutting off the sup- 
ply of compressed air from the chamber V and permitting the 
air to escape at b. It will be noted that air is continually 
escaping at K during the time the room is too hot, but this is 
a very short interval as compared with the entire time, and 
moreover the oritice at A' is exceedingly small, so that the loss 
of air is quite insignificant. It will also be noted that with this 
ipparatus the damper is quickly moved from a position fully 





Fir.. 187. — Johnson Positive Thermostat. 



Open to shut, or vice versa, and that it will not stand in an 
intermediate position. 

The manufacturers of the Johnson thermostat have quite 
recently designed an instrument which will move the adjusting 
damper connected to the line A'A" slowly and will hold it in 
any intermediate position as desired. This is considered an 
advantage for systems of ventilation in which it is always desired 
to admit the same volume of air, but in which the relative 
amounts of hot and cold air are varied to maintain the desired 
temperatiu'e. 

The Johnson Positive Thermostat. — In the accompanying 
the curved metal strip T is the element affected by 



450 



HEATING AND VENTILATING. 



the rcxmi temperature. A slight change in temperature imme- 
diately aSects the strip and the movement causes it to either 
open or close the small air port C. When this port C is 
open, a small amount of air escapes, but when the strq> 
closes the port, it causes a pressure to collect on the diaphri^m 
B. This pressure forces out the knuckle movement, whidi, 
when it passes the center position, instantly pushes in the 
valve V. This movement of valve V immediately releases 





Fig. i&S. — Johnson Intermediate Thermostat. 



the air pressure in the branch line, permitting the radiator 
valve to open. 

When T expands outward, the air pressure oa B is 
relieved, the valve V is instantly thrown outward, and the 
full air pressure is at once turned into the branch line to close 
the radiator valve. 

The Johnson Intermediate Thermostat. — The thermostatic 
strip T moving inward or outward, as affected by the 
room temperature, varies the amount of air which can escape 
through the small port C. When the port C is completely 
closed the full air pressure collects on the diaphragm B, 



TEMPERATURE REGULATORS. 451 

which forces down the main valve, letting the compressed air 
from the main pass through the chamber D into chamber £, 
as the valve is forced off its seat. The air from chamber 
E passes into the branch to operate the damper. 

When port C is fully open, the air pressure on diaphragm B 
is relieved, the back pressure in E lifts up the diaphragm 
and the air from the branch escapes out through the hollow 
stem of the main valve. The thermostat thus operates on a 
reducing valve principle which insures various pressures as 
required in the branch line to operate the damper. 

217. Humidity Regulators. — ^Automatic devices have re- 
cently been perfected for varying the moisture content of the 
air automatically so as to maintain it at any desired percentage 
of humidity. This apparatus works on the principle of a double, 
differential thermostat, one part of which is moved by the 
temperature of the wet bulb thermometer and the other by the 
temperature of the dry bulb thermometer in such a way as 
to give a differential action arranged to supply or cut off the 
supply of moisture as desired to maintain a constant per- 
centage of humidity corresponding to a constatit temperature 
difference between a dry and wet bulb thermometer for a given 
temperature. One type is described in Chapter XX on Air 
Conditioning. 

218. Saving Due to Temperature Regulation. — The expense 
of constructing a perfect system of heat-regulation is met in 
a short time by the saving in fuel bills. The writer recently 
examined the records of the fuel consumed in a building when 
heated for a series of years without, and afterwards with, the 
heat-regulating system. He also examined the records show- 
ing the coal consumed in two buildings of exactly the same 
size and class, in the same city, and as nearly as possible with 
the same exposure. In both these cases the saving was some- 
what over 35 per cent annually of the cost of the regulating 
apparatus. 

The saving in any given case must, of course, depend upon 
conditions and how carefully the drafts are regulated under 
ordinary systems of operation. UsuaUy, when the temperature 



452 HEATING AND VENTILATING. 

m 

is regulated by hand, the rooms are allowed to become alter- 
nately hot and cool, but a greater portion of the time they are 
much warmer than is necessary*, and frequently windows arc 
opened for the escape of the extra heat. The maintenance of 
a uniform temperature for such cases means a saxdng of fuel 
by utilizing the heat better, and usually, also, by a more perfect 
combustion of fuel. It would seem from these considerations 
that a reasonable estimate of the sa\ing obtained by the use of 
a perfect temperature regulator, as compared with ordinary 
regulation, would run from 15 to 35 per cent of the fuel bills 
per year. 



CHAPTER XVIII. 
SCHOOLHOUSES, SHOPS AND GREENHOUSES. 

219. Schoolhotise Wanning and Ventilation. — ^The warm- 
ing and ventilation of school buildings constitutes one of the 
most important applications of the art and involves a practical 
exposition of all the scientific principles relating to the sub- 
ject. The best general discussion of the application of this 
science is to be found in a treatise written by Professor S. H. 
Woodbridge of the Massachusetts Institute of Technology for 
the Connecticut State Board of Education in 1898 and from 
which extracts are here reprinted by permission. 

220. Complex Character of the Problem. — ^What the respir- 
atory system is to an animal the ventilating system is to a 
building. As the habits of an animal determine the type 
of respiratory system most appropriate to it, so the type and 
use of a building are the principal factors in determining the 
characteristic features of the ventilating system best adapted 
to it. The large and modern high school building presents 
a complex type far removed from the simpler patterns, found 
in the dwelling-house, the office building, ,the audience-hall, 
the church, or even the theatre. It presents an involved 
combination of rooms designed for widely different purposes, 
each room requiring an equipment adapted to its special use, 
and the building as a whole demanding a treatment with proper 
reference to its periodic use and its peculiarities of arrangement 
and exposure. Between the complex problem peculiar to such 
a building and the simple one presented by the one-room school- 
house at a country cross-road there exists a range of type com- 
pletely filling the interval, each step of the gradation necessitat- 

453 



454 HEATING AND VENTILATING. 

ing a corresponding modification in the method of, and means 
for, ventilation. 

221. Relation of Pure Air to A^tality. — Air is as essential to 
the products of physical and dependent mental energy as 
it is to the intensity and brilliancy of a candle-flame. The 
breathing of impoverished air results of necessity in the dull- 
ing of the vital fires of the body and of the keen edge of the 
intellect. It means a weakened body and a dulled mind. 
A lowered vitality of the body, besides exposing it to an increased 
liability to communicated, contracted, or constitutional disease, 
also impairs its effectiveness as a vital mechanism. The 
aggregate of physical and mental vitality lost through ignorant 
or indifferent regard, and even culpable disregard, of the exact 
and delicate dependence of the activities of body and mind on 
the maintenance of a normal, including atmospheric, environ- 
ment, surpasses all common conception or belief. That air 
quality is fully as important as food quality in the production 
of vital energy is a conception which has yet to be borne in 
upon the public, if not the professional, belief and conscience. 

222. Limitations to the Supply of Pure Air, — ^A rule which 
may be safely insisted upon for general adoption and applica- 
tion is that pure air should be supplied to enclosures in the 
maximum rather than in the minimum quantity tolerable. 
Only two considerations should be allowed to limit the quantity 
of air-supply: air-draughts and bank-drafts. 

Draughtiness in air-currents is more dangerous to health 
than the ordinary ^vitiation of air ih badly ventilated enclosures. 
On the other hand, the warming and, under some circum- 
stances, the moving of air in large quantities for ventilating 
work is far from costless. Both draughtiness in air movement 
and costliness in the warming of air put, therefore, a deterring 
limit on air quantities to be used in practical ventilating work. 

223. Draughtiness in Large Halls. — With a given hourly per 
capita air-supply, the danger from draughtiness within an 
enclosure increases, approximately, inversely as the per capita 
space. Fortunately, however, the necessity and importance 
of ventilation are not the same for crowded as for sparsely 



8CH00LH0USES, SHOPS AND GREENHOtJSES. 455 

occupied rooms, being of least account in rooms intermittently 
occupied, and of greatest account in those most continuously 
used. The length of time for which a person is exposed to 
the confined air of an enclosure is, therefore, an essential factor 
in determining the proper rate .of its ventilation. The harmful 
effects of short exposure to impure air once a week are small 
when compared with those incurred by frequent and protracted 
exposure to such air. In effect, the time of actual occupancy 
varies with the provided per capita space; and, for equal 
hygienic results, the per hour and per capita air-supply required 
also vary in the same manner. Considering only permanent 
effects on health, and individual air-supply of iocx> cubic 
feet per hour furnished to a crowded audience-hall having 
but loo cubic feet space per capita, may, therefore, be regarded 
as equally good ventilation with 3000 cubic feet per capita 
supply of air per hour furnished to a schoolroom having 300 
cubic feet per capita space. For the ventilation of crowded 
rooms the air- volumes usable are limited by draught dangers; 
and for ventilating less and the least crowded rooms the 
quantities are limited by the cost. It is the office of the 
architect and the engineer to provide for the rooms of the first 
class a maximum air-supply with a minimum of draught; and 
for rooms of the second class the freest ventilation consistent 
with reasonable expense. 

224. Means for Reducing Draughtiness. — The audience- 
halls and larger lecture-rooms of schoolhouses cannot generally 
be provided for as perfectly as can similar rooms having fixed 
seats or desks, the usual or specially provided surface of which 
may be utilized for a diffusive entrance of large quantities 
of air. The floors of these large rooms must at times be cleared 
for drill, dancing, and social occasions. Danger from draughts 
xnust, therefore, be reduced by dividing the inflow into as many 
^Knd small and slow-moving currents as practicable, and by 
ving to the inlets such positions and formations as shall deliver 
air in directions least liable to produce sensible draughtiness. 
animal heat yielded by a crowded audience is frequently 
than that lost through walls, windows, and other means. 



466 HEATING AND VENTILATING. 

The effect of that heat is to raise the temperature of the audi- 
torium air and to necessitate a temperature of air-supply lower 
than the temperature of the room. Because of the need of 
this low temperature, it is desirable to give to the entering 
currents of air a direction which shall as much as possible 
prevent their dropping floorward, at least in concentrated form. 
If the air-supply must be admitted through wall apertures, 
they should be elevated, unless they are made so large as to 
reduce the rate of inflow to or below a linear rate of 30 feet 
per minute. Even when the wall openings are elevated, the 
currents should be given an initial upward direction. They 
will thus take a longer path before reaching the floor, and 
will, therefore, mix more thoroughly with the warm air of the 
room by being longer in contact with it, and by flowing more 
diffusively through it. If the air-inlets to a room of this 
character can be placed in the floor and protected from infall- 
ing dirt, that position is preferable to a wall location. In 
general it may be said that wall inlets through which air issues 
with rapid or even moderate movement and at temperatures 
from 100° downward should be elevated well above the head 
plane for the purpose of giving the currents a location in the 
unoccupied parts of a room. By means of chutes of solid .or 
open material, the entering air may be given a slight or sharp 
upward course. By completely covering the inlet with a 
semi-cylindrical surface of fine wire gauze or other impervious 
material, of any size desired, the entering air may be made to 
move radially from the inlet in a more or less horizontal plane, 
and with a velocity varying with the extent of the diffusing 
surface, and with the volume of air issuing through it. By 
deflecting plates or blades set to separate the current and to 
throw the entering air in divergent directions, the inflow may 
be given a radial direction from the inlet, both laterally and 
vertically if desired. Blades are preferable to gauze, as the 
meshes of the latter fill, and, even when clean, offer sensible 
resistance to air-flow. Blades are as effective in breaking up 
the larger current into a number of divergent ones, and produce 
a quicker and more thorough diffusion of air throughout a 



8CHOOLHOUSE8, SHOPS AND GREENHOUSES. 457 

room. The form of diffuser must be chosen with reference to 
the location and surroundings of the inlet. Properly made and 
used, diffusers make impossible a processional of air from inlet 
to outlet that does no effective ventilating work. 

The rapidity of air-flow through supply-flues has obviously 
no necessary effect upon draughtiness within rooms. By the 
use of suitable diffusing means, air, although brought to the 
diffusers with a relatively high velocity, may yet by them be 
given such reduced velocity and dispersed movement as to 
remove all danger from this cause. 

225. Little Draughtiness in Outflowing Currents. — For the 
protection against draught due to outward movement of air 
from rooms less precaution, is needed. The movement of 
escaping air is slowly accelerated toward the location of the 
discharge, the velocity of the movement toward that point 
decreasing inversely as the square of the distance from it. 
The air-movement, therefore, being convergent for a wide 
range, is the reverse of the divergent inflow produced by the 
use of deflecting plates or diffusing surfaces, and is wholly 
unlike the concentrated and continuous current projected from 
a supply-register. It is necessary only that the area of the 
outlets should not be too large, the volume of air-movement 
too great, the final velocity of air-approach too rapid, and 
that permanent sittings should not be placed too near the out- 
lets. 

226. Air-supply for Schoolroom. — In the case of a school- 
room, the per capita floor and cubic space is generally from 
two to three times that conunon in well-filled audience halls. 
To such a room, having a cubic space of from 11,000 to 12,000 
feet, and seating from forty-five to fifty scholars, it is practicable 
to supply without draughtiness and without the use of excep- 
tional precautionary means for preventing it, from 2000 to 
2500 cubic feet of air per hour to each occupant, or a total 
hourly quantity of from 100,000 to 125,000 cubic feet, the 
larger quantity being more than one-sixth of the contents of 
the room per minute. When special means are provided 
for a draughtless entrance and removal of air these quantities 



458 HEATING AND VENTILATING. 

may be largely increased. Between 90 and 100 cubic feet per 
minute for each sitting have been passed through the class- 
rooms of a schoolhouse equipped in accordance with modem 
methods, and there was no complaint of draughts. Usually, 
however, the limit of immunity from draughts is reached when 
the rate of air-supply is brought up to an equivalent of ten 
changes per hour. 

227. Cost. — The expense of ventilation properly includes 
the cost of all special building arrangements and construction 
provided; of all special equipment for heat production and air 
warming; of power for moving, distributing, and removing the 
air; of fuel for warming; and of specially skilled attendance 
required above that called for in ordinary heating work. 

228. Methods of Saving Heat. — It is now intended to set 
forth in detail various opportunities for econotny in methods 
as illustrated by the special characteristics of schoolhouses. 
The several means for special economy in the warming and 
ventilating of schoolhouses will accordingly be discussed under 
the following heads: successive ventilation; quick preparator>' 
warming; warming by rotation; heat commonly wasted; 
solar heat; automatic control of temperature; double glazing; 
double sashing; waste of heat at night; plenum and vacuum 
methods; location of inlets and outlets. 

229. Successive Ventilation. — The first suggestion made 
in the interest of economy relates to a method for the successive 
use of one and the same volume of air, first for the free ventila- 
tion of the least occupied parts of a school building, and then 
for the ventilation of those rooms in which the vitiation of 
air is either excessive or else of obnoxious quality. The parts 
of buildings, especially in those designed for use as high or 
normal schools, which are not closely occupied, frequently 
aggregate as much in space as the classrooms themselves. 
Such parts of a building are generally continuously ventilated, 
though perhaps infrequently occupied. No amount of instruc- 
tion or training of janitors and engineers is likely to result in 
a continued practice of opening and closing dampers or registers, 
according to the occupied or unoccupied condition of rooms. 



SCH00LH0USE8, SHOPS AND GREENHOUSES. 459 

However carefully such precautions may be taken at first, 
they are likely to be eventually abandoned, and the ventila- 
tion of the entire building to become continuous during school 
sessions. It is this continuous ventilation of large parts of 
the building outside of classrooms which greatly increases 
the apparent cost of classroom ventilation, and which justifies 
the use of economic methods for the ventilation of rooms not 
continuously occupied. Besides the provision to be made in 
school buildings of higher grade for such rooms as audience 
halls, lecture rooms, recitation and classrooms, gynmasiums, 
and laboratories — all of which, when in use, require, in the 
order given, increasingly large per capita supplies of air — ^are 
the coat, lunch, bath, lavatory, and sanitary rooms, and the 
private and retiring rooms, each requiring its own appropriate 
treatment. Unquestionably, a generous and continuous flush- 
ing of all these apartments with the purest air would prove 
hygienically advantageous and financially disastrous. In every 
case there is at some point of ventilating work a balance between 
hygienic gain and financial loss. 

Only in cases of special impurities or of abnormal or disease- 
producing contents given to, and carried in, the air of an enclosure, 
or in cases of prostrated vitality requiring the utmost oppor- 
tunity for recovery, is there commensurate gain in providing 
more than 50 cubic feet of air per capita per minute for breathing 
purposes, provided, of course, that such air is effectively used. 
For ordinary schoolroom work even that quantity cannot be 
safely urged unless assurance is given of the purpose and ability 
of its users to make ventilation draughtless. 

230. Supply of Air for Rooms not Frequently Occupied. — 
The quantities of air which should be furnished by ventilat- 
ing means cannot be safely based solely on the number of 
those to occupy the rooms to be provided for. The most 
active and dangerous impurity in the air of occupied enclosures 
is the matter of organic nature, called effluvia, thrown off by 
the body through its pores. That matter rapidly changes in 
cliaracter, passing through a fermenting and decomposing to a 
^putrescent condition. The longer it is retained within a room, 



460 HEATING AXD VENTILATING. 

the worse its odor becomes and the more morbific its condition. 
The aims of ventilation should be, as far as practicable, 
to limit atmospheric impurities to the location of their origin, 
and to reduce the quantity and the time of retention of such 
impurities within an enclosure to a minimum. In proportion 
as the per capita space of an enclosure is greater, the quantity 
of such matter contained in it is large, the time of its retention 
longer, and its character more offensive and harmful. It 
follows, therefore, that the more sparsely occupied rooms of a 
building are those to which the largest per capita supply should 
be furnished. Laboratories in which gas is burned and in which 
vapors, fumes, and gases are generated in any considerable 
amount outside of hoods also belong to the class of rooms needing 
more air per occupant than do classrooms. The same is true 
of gymnasiums, physical-training rooms, and playrooms, for 
vigorous physical exercise produces a condition of the body 
calling for a larger air-supply than the condition of repose 
demands. 

231. Course of the Air-supply. — The ventilation of corri- 
dors should be sufficiently free to fill them with air suitable for 
passage to, and use in, class or other rooms. The continuously 
or frequently opened doors or transoms between corridors and 
rooms make the continuous or occasional mingling of corridor 
air with that of rooms probable and almost inevitable. The 
passage from such an accidental to an intentional use of hall- 
ways for fresh-air reservoirs and channels is both legitimate 
and proper. Playrooms, lunch rooms, g>Tnnasiums, and other 
rooms of their general type, though intermittently occupied 
and sometimes crowded, belong, because of their average con- 
dition, to the sparsely occupied class of rooms. Continuously 
and separately to ventilate them on the basis of the largest or 
the ordinary numbers occasionally occupying them would 
require great volumes of air. Such rooms and parts of build- 
ings may, however, be ventilated in series, or by a successive 
method, which will meet the requirements of their shifting 
groups of occupants, and yet require the use of relatively small 
volumes of air. Coat, bath, lavatory, and sanitary rooms 



SCHOOLHOUSES, SHOPS AND GREENHOUSES. 461 

need no independent supply of purest air. Air pure enough 
for breathing purposes in schoolrooms is certainly suitable for 
airing wraps hung in coat rooms. The air which passes out 
from schoolrooms through discharge-flues is, generally speak- 
ing, as pure as that surrounding the occupants of the rooms. 
Stigmatized as foul only as a matter of convenience to distin- 
guish it from the air-supply, it is popularly supposed to become 
so by virtue of its entrance into the way of the outcast^ 
Lavatory, bath, and sanitary rooms are, from a hygienic point 
of view, most suitably treated when they are atmospherically 
isolated from other parts of a building, as when ventilated by 
strong aspirating currents which cause air to move toward and 
into them from adjacent apartments, and prevent air-movement 
from such rooms to those apartments. Classrooms may be 
vented, in part at least, through their coat rooms. Lavatory, 
bath, and sanitary rooms may take their air from the supply 
which has done its partial ventilating work in the hallways, 
playrooms, and other permanently or periodically occupied 
rooms. For that purpose air may be continuously supplied in 
generous quantities to plajnrooms, lunch rooms, physical- 
training rooms, or gymnasiums, which are in the basement, 
and which are occupied but a small fraction of the time. From 
these rooms the air may be sent to ventilate the corridors of 
the building, rather than being immediately thrown away. 
The corridors are by this means flushed with fresh air which 
should find egress, not through the roof nor through outlets or 
windows on the upper floor, but rather through the lavatories 
and sanitaries. If the air-supply is generous enough, as it may 
be made to be, it may be sent from the corridors to the class- 
rooms, and thence to the coat rooms. Thus in successive 
ventilation the movement of air must be from locations of 
lesser to those of greater vitiation, as from playrooms to corri- 
dors, from classrooms to coat rooms, or as from the corridors 
through playrooms to sanitary rooms. 

When at recess scholars leave classrooms for play or lunch 
rooms the conditions described above are in part temporarily 
reversed. The crowds are then in the basement, and the 



462 HEATING AND VENTILATING. 

corridor air contains impurities brought from the crowded 
basement rooms. Meanwhile, however, the vacated class- 
rooms are being flushed by their independent and uninterrupted 
air-supply, and at the same time the large volume of corridor 
air is so diluting the impurities carried upward from the base- 
ment that they become imperceptible, if, indeed, they are at 
all noticeable even in the basement rooms themselves. In 
this successive method, then, basement rooms and corridors, 
sanitary rooms, and coat rooms, may be effectively ventilated 
by moderate quantities of air as compared with the volume that 
would be required if each part were as effectively and contin- 
uously ventilated by independent means. 

232. Quick Preparatoiy Wanning. — The heat quantity 
necessary for the preparatory warming of a building varies 
greatly with the methods used. In the first place, the heat 
expenditure is approximately proportional to the time given to 
the wanning process. The quicker the process, the less the 
fuel required. During the process of warming, heat is lost by 
its transmission through walls find by air-leakage. For rapid 
heating the production and distribution of heat must be large 
and quick. A heating apparatus of low power, although 
economical in its first cost, is, in the end, expensive, because 
it is unequal to such a demand. A heating system successfully 
planned with reference to maintaining both an internal tem- 
perature of 70° against an outside temperature of zero, and also 
a generous ventilation at such times, is equal to the demands 
of such work. 

233. Warming by Rotation. — Relatively little heat and time 
are required to warm the air of a building as compared with 
the heat and time needed for warming walls, floors, ceilings, 
and contents. The warmer the air entering the heating bat- 
ter>% the higher :ts temperature is on leax-ing it, and the amount 
of heat required to bring that air to a given temperature is cor- 
respondingly less. A considerable gain is, therefore, made 
when, for the purpose of warming a building, air is taken from 
the building itself, rather than from the colder outside supply. 
The method of warming a building in this way is one of rota- 



SCH00LH0USE8, SHOPS AND GREENHOUSES. 463 

tion: the air is taken from the building, heated, distributed to 
the rooms, and, after yielding considerable of its heat to the 
room surfaces, is brought back to the heating battery either 
by means of a special arrangement of flues, or by the use of 
the corridor-waj^ and stairwells. Wanning by rotation should, 
of course, cease and ventilation should begin before a building 
is occupied. 

234. Heat Commonly Wasted. — ^Heat usually wasted is 
the spare heat of boiler-gases escaping through the smoke- 
pipe. This may be used for strengthening draughts through 
vent-stacks, and thus the making of heat especially for that 
purpose is rendered unnecessary. This spare heat may also 
be made available for strong ventilation of sanitary rooms or 
any other equally important work. For this purpose the chim- 
ney and the ventilating stack about it should be designed with 
reference to the transfer of the needed amount of heat from the 
combustion gases to the vent-flue air. In all such work care 
should be taken not to reduce the temperature of the com- 
bustion gases so as to jeopardize the chimney-draught. Still 
another form of heat usually wasted is that of fires banked for 
the night, this heat being generally expended in useless steam- 
making in closed boilers. Such steam may be used in limited 
and subordinate parts of the heating system, as in the foot- 
warmers, hallway coils, heaters in sanitary rooms for the pro- 
tection of fixtures against freezing, and for other like work. 
Provision for these uses may be made in any steam system 
through suitable supply- and return-pipe connections with the 
boiler. 

235. Solar Heat. — Solar heat is a factor to be regarded in 
the planning of a warming and ventilating system. It may be 
demonstrated by^ a properly protected thermometer that the 
average day temperature of air is higher on the south than on 
the north side of a building. The difference often reaches 
10°. An average of 5° would make it highly advantageous to 
take the air for ventilating work from the south rather than 
from the north side of a building. If an average rise of 35° is 
needed in the air temperature in ventilating work, then one- 



464 HEATING AND VENTILATING. 

seventh of the heat required for that rise could be gained by 
choosing a south as against a north location for the inlet. 
Such a location is possible only when mechanical ventilation is 
used, for in gravity work it is necessary to place the inlet 
on the side of the building toward the prevailing winds of 
winter. 

236. Automatic Control of Temperature. — From a hygienic 
point of view the close regulations of the temperature of a 
building is important; and from an economic point of view 
it is even more important, when the air-volumes used are large. 
Such regulation cannot be safely entrusted to teachers who, 
absorbed in their work, fail to note a change in temperature 
until it becomes suflSciently extreme to extort notice. A 
radical and speedy change being then called for, windows and 
doors are resorted to until rooms become chilly. The inevi- 
table results of such methods of regulating the temperature are 
wasteful escape of heat and disastrous catching of colds. The 
quantity of heat may be closely regulated by automatic means 
which control either the flow of steam or hot water into the 
heaters, or the proportions in which cold and hot air are mixed 
to produce the temperatures required. Such control is as essen- 
tial to the evenness of temperatures furnished by a heating sys- 
tem and to the economy of its working as is a governor to the 
steadiness and the economy of the working of an engine. The 
importance and reliability of the control in these essential 
particulars are fully established. That reliable results are 
obtainable with the best forms of apparatus properly installed, 
cared for, and used, has been abundantly demonstrated. Aside 
from the undoubted value of a reliable system for control of 
temperature in protecting health and in sustaining vigor, its 
service in economizing fuel is important. 

237. Double Glazing. — As heat loss through the glass of 
windows is generally about four times that through equal areas 
of walls, a double glazing in windows is advantageous. The 
two panes, thoroughly clean, can be puttied in, one on the 
outside and one on the inside of a sash, with a space between 
them of from one-fourth to one-half of an inch. If the work 



8CH00LH0USES, SHOPS AND GREENHOUSES. 465 

is reasonably well done, the inside surfaces of the panes will 
remain clean indefinitely. Double glazing stands between 
cold temperature on the outside of a building and the desired 
temperature on the inside, and so is as efifective upon one side 
of a building as another. If day and night are included, the 
diflferences in temperature between the north and south side are 
not great. The saving in heat by double glazing can be made 
to approximate 33 per cent of the heat escaping through single- 
glazed windows; the saving in fuel approximates 2 poimds 
per hour for every 1000 square feet of windows. 

238. Double Sashing. — Double windows are more efifective 
than double glazing in preventing heat waste. They protect 
against both inside and outside diflferences of temperature, and 
also against the inward leakage of cold air resulting from 
pressure due either to inside and outside temperature diflferences 
or to wind action. They are, therefore, doubly serviceable. 
They are more efifective on the prevailing windward side of a 
building than on its leeward side. 

239- Waste of Heat at Night. — ^To carry over from one 
day to another as much as possible of the heat of a building 
some of which is stored in its air and much more in its walls, 
the building' should be closed as tightly as practicable when 
not in use. The in-leakage of air through walls and windows 
is far more rapid than is usually supposed. Recent experi- 
ments made in a building of ordinary schoolhouse construction 
indicate that in mildly cold and quiet weather such leakage 
equals the cubic contents of a room or building approximately 
once in each ninety minutes. In sharply cold weather it is 
greater, and still more so in windy weather. Air-leakage is 
the unknown and most disturbing factor in estimating the 
required power of heating-plants. Unless such leakage is to 
be relied upon as a factor in ventilation, it should be made as 
small as possible. To reduce loss of heat at night, and when- 
ever the building is closed, the vent flues or shafts should be 
closed by dampers at their tops. 

240. Plenum and Vacuum Methods. — For the same reason 
discharge ventilation should not be made in excess of the 



466 HEATING AND VENTILATING. 

supply. The supply should, on the other- hand, be in sufficient 
excess of the discharge to produce a slight pressure or plenum 
condition, particularly within the lower rooms of a build- 
ing. A vacuum condition within rooms augments the inward 
movement of cold air through walls and windows, and tends 
to cold floors and chilly rooms. No system of ventilaticm 
should be installed which prevents the windows being opened. 

241. Location of Inlets. — ^The efficiency of a ventilating 
system has an important bearing on the cost of obtaining the 
results for which it is provided. The air quantity used does 
not determine the thoroughness of the ventilating work it 
effects. As the Gulf Stream goes through the Atlantic, so air 
often goes through schoolrooms, its ventilating effectiveness 
ranging as low as from 36 per cent to 40 per cent out of a 
possible 100 per cent. The location of outlets and the con- 
centrated or diffused movement of air through rooms are the 
chief determining factors in the problem. 

242. Local Ventilation. — Strong local exhaust is required 
in certain parts of schoolhouse ventilation. Where ventilation 
can be effected by the immediate removal of atmospheric 
impurities, a great gain is made by doing so. To remove com- 
pletely the smoke of an open Are burned in a brazier placed 
in the middle of a room would require a himdred or a thousand 
times more air than if that fuel were burned in a fireplace. 
The air of a chemical laboratory may be kept as clear as that 
of a classroom and with no greater per capita supply, if all 
fimiing work is done under hoods. If such work is generally 
done in the open rooms, ten times that volume of air passed 
through them might not clear the air. The discharge from 
such rooms should be largely, if not chiefly, through the hoods; 
and the airways through and from the hoods should be designed 
and furnished with reference to that purpose. So also the 
general ventilation of sanitary rooms should be largely by means 
of strong local discharge through the fixtures of both closets 
and urinals. If the discharge ventilation is not effected by 
mechanical means, the vent-flues of lavatories, sanitary rooms, 
and hoods of lunch-room ranges should be made warmer than 



SCHOOLHOUSES, SHOPS AND GREENHOUSES. 467 

the flues of other rooms. In this way a movement of air toward 
and into the rooms which are to be locally ventilated is produced, 
counteracting and overcoming any conflicting pull of flues 
which discharge air from other parts of the building. The 
location of chemical laboratories, of kitchen schoolrooms, and 
of other rooms of similar character should be on. the top floor, 
since the trend of air, especially in cold weather, is upward 
through a building. When such rooms are thus situated, 
fumes, gases, and odors generated within them are more com- 
pletely confined to the place of their origin than was ever possible 
when these rooms were placed, as was formerly the custom, in 
the basement. 

243. Air Filtration. — The importance of filtering (or washing) 
the air supplied to school buildings varies with local conditions. 
In dusty or smoky localities such filtering may be essential to the 
cleanliness of a building and to the protection of its contents. 

244. Heating of Greenhouses. — Greenhouses and conserv- 
atories are heated in some cases by steam and in other 
cases by hot water, and there is quite a difference of opinion 
held by florists respecting the relative merits of these two 
methods of heating. The fact, however, that either system 
when properly proportioned and well constructed gives satisfac- 
tory results indicates that the difference is not great, and that 
the relative value may depend entirely on local conditions. 

The methods of piping employed may in a general way be 
like those described, and the pipes may be located so as to run 
underneath the beds of growing plants, or in the air above, as 
bottom or top heat is preferred. In many cases large cast-iron 
pipes, the method of erection of which is described in Chapter 
VI, are used in hot-water heating of greenhouses. These are 
generally located beneath the beds of growing plants; the 
main flow- and return-pipes are laid in parallel lines, with an 
upward pitch from the boiler to the fartherest extremity of the 
house. Recentiy small wrought-iron pipes have been used 
extensively for greenhouse heating. In this case the main 
pipe has generally been run near the upper part of the greenhouse 
and to the farthest extremity in one or more branches, with a 



468 HEATING AND VENTILATING. 

pitch upward from the heater for hot-water heating and nitfa 
a pitch downward for steam-heating. The principal radiating 
surface is made of piarallel lines of ij-inch. or larger, pipe, 
placed under the benches and supplied by the return current; 
this has in all cases a pitch toward the heater. An illustration 








I -i 


K 


c 





Fig. iSS. — Plan and Elevation of Imping. 

of the method of piping as designed by A. H. Dudley of the 
HcR-ndcen Mfg. Co. is shown in the three following figures 
so clearly as to require no special explanation. 

Any sjatcm of piping which gi\cs free circulation and 
which is adapted to the local conditions will give satisfactory 
results. The dirt-clions for erecting and taking off branches are 
thir same as in rciidcncL- heating. 



SCHOOLHOU8E8, SHOPS AND GREENHOUSES. 469 

Proportioning Radiating Surface, — The loss of heat from a 
greenhouse or conservatory is due principally to the extent of 
glass surface; hence the amount of radiating surface is to be 
taken proportional to the equivalent glass surface, which in 




Fig. 289. — Piping for Outside Bench. 




Fig. 290. — Piping for Inside Bench. 



every case is to be considered as the actual glass surface plus 
i the exposed wall surface. From this surface about i heat- 
unit will be transmitted from each square foot for each degree 
difference of temperature between that inside and outside per 
hour; that is, if the difference of temperature is 70 degrees, 



470 



HEATING AND VENTILATING. 



each square foot of glass surface would transmit 70 heat-units 
per hour. The radiating surface usually employed for this 
purpose is horizontal pipe, and hence is of the most efficient 
kind. From a surface of this nature we can consider without 
sensible error that 2.2 heat-units are given off from each square 
foot for each degree difference of temperature between the 
radiator and the air of the room per hour. From this data a 
table can be computed which gives the ratio of equivalent glass 
surface to radiating surface, in which the results will be found to 
agree well with average practice; the results are to be increased 
or diminished 10 to 20 per cent, according as the circumstances 
of exposure or the quality of the building vary more or less 
from the average condition. 

TABLE SHOWING AMOUNT OF GLASS SURFACE OR ITS EQUIVALENT 
WHICH MAY BE HEATED BY ONE SQUARE FOOT OF RADLATING 
SURFACE IN GOOD BUILDINGS. 



Temp, of Radiating Surface, Deg. F. 



Temp, of surrounding air, 90** F. . 

** 80° F.. 



<c 
f c 
f ( 
(( 



<( 
(( 
(< 
(( 



70* F. . . 
6o*F... 
SO* F. . . 
40* F. . . 



Hot Water. 



160' 



180' 



200^ 



5 lbs. 227' 



10 lbs. 240' 



Square Peet of Glass for i Square Foot of 
Radiating Surface. 



1.9 
2.3 

30 
40 

SO 

6.9 



23 


2.8 


3 3 


3-8 


29 


3 5 


40 


4.6 


36 


42 


SO 


5.7 


4-6 


5-2S 


6.0 


70 


6.0 


6.8 


8.0 


9.0 


8.0 


8.2 


10. 


" S 



From the data above the following table is computed, 
which gives the radiation in square feet required for green- 
houses or conservatories with different amounts of glass sur- 
faces. It also gives divisors from which the heating surfaces 
or grate surfaces in the boilers may be computed by dividing 
the given amount of radiation. Thus for a greenhouse with 
1000 feet of glass surface, which is to be kept at 70 degrees in 
the coldest weather, we note in the table that 200 square feet 
of radiation will be required; the heating surface in the boiler 



8CHOOLHOUSE8, SHOPS AND GREENHOUSES. 471 

will be 200 divided by s-6( = 36) square feet, and the area of 
grate will be (200 divided by 156 = )!. 28 square feet. 



GREENHOUSE HEATING WITH STEAM. 



Rmdifttaan required, iq. ft., 

IUdl"tlon*^iiir^; 'vi.' ft.', 

RftdUtiao requind, aq. ft,. 

Umpt. 60 

Radittiini nqnired, iq. ft,, 

n requind, eq. ft.. 



7oi heating nufaci 



GREENHOUSE HEATING WITH HOT WATER. 



8qum fert of bIbh 


100 


.so 


S» 


7SO 


1000 


,S0O 


«« 


.SOO 


JOOO 


4000 


s«o 


.o.ooo 


Wolir ISO' 


























" :: " E;:: 


1! 
31 


61 

01 




Z 


i 


111 

3M 


ttbt 


S]3 


46c 
U.IO 


ii 


Ififtl 


ilooo 

l.SM 
J. 33 J 


DitUor> of hadialion 


























For heiHrgi «,ri»« 




6.S 


r.6 


B.l 


a,. 


lil 


%i 


t»i 


3M 


'U 


'SiS 


3to 





The sizes of main pipes should be the same as those which 
are used for direct heating. 

Relative Tests of Bot-water and Steam Heating Plants. — 
Several tests have been made to determine the relative efficiency 
and economy of steam and hot-water heating plants. The 
first test so recorded was made at the Massachusetts Agri- 
cultural College by Professor S. T. Maynard, the results of 
which are given in Bulletins 4, 6, and 8, issued by the Mass. 
Exp. Station, 1889 and 1890. In this test two houses were used 
which were located as nearly as possible with equal exposure, 
and the tests were made with great care and by entirely di^n- 
terested observers. The following is a summary of the results 
and conclusions as taken from the bulletins: 



472 HEATING AND VENTILATING. 

STEAM-HEAT VERSUS HOT-WATER. 
[From Bulletin No. 4.] 

In order to get at some facts in regard to this subject, so important to 
the grower of plants under glass, and gain some positive knowledge as 
to the relative value of the two systems, two houses were constructed 
during the summer of 1888, 75X18 feet, as nearly alike as possible in every 
particular. Two boilers of the same pattern and make were put in, one 
fitted for steam and one for hot water; the steam for heating the east 
house, and the hot water for the west and most exposed one. The boilers 
were completed and ready for work in November and were used until 
January 9, 1889, when these experiments began. 

Records of temperature of each house were made at 7.30 and 9 a.m., 
and 3, 6, and 9 p.m. Sufficient coal was weighed out each morning for the 
day's consumption and the balance not consumed deducted the next 
morning. " The two boilers and fittings were put in so as to cost the 
same sum and were warranted to heat the rooms satisfactorily in the 
coldest weather." 

These experiments were repeated during the months of January and 
February, 1889, and in summarizing the results it was found that the steam- 
boiler consumed during the two months referred to 6582 lbs. of coal while 
the hot-water boiler consumed in the same time only 5174 lbs., a saving 
in favor of the latter of nearly 20 per cent. At the same time the temper- 
ature of the room heated by hot water averaged 1.7° higher than that 
heated bv steam. 

The temperature was more even where heated by hot water, and con- 
sequently there was less danger from sudden cold weather. This was 
strikingly shown on the night of February 22. 

The average outside temperature for the day was 34°. 

At 9 P.M. it was above 32°, and proper precautions not having been 
taken for so sudden a change as followed (the average temperature during 
the 23d of February was 2°), at 6 o'clock on the morning of the 23d the 
temperature of the room heated by steam was 29°, while in that heated 
by hot water it was 35°. . . . 

[From Bulletin No. 6.\ 

The boilers used were built of cast-iron sections. In the hot -water 
boiler five sections are used, the area of heating surface exposed to the 
fire being 74.5 feet. 

The steam-boiler consists of eight sections, the total heating surface of 
which is 85.12 feet. 

The experiments reported in the April Bulletin were continued during 
the two following months of March and April, and from the tables show- 
ing the comparative results the following summary is appended: 



8CHOOLHOU8E8, SHOPS AND GREENHOUSES. 473 



SuuuASY JOB. Hot-water Boiler. 
Total coal consumed by hot-water boiler from December 33, 1888, to 
April 34, 1889, 4 tons 1155 lbs. Average daily temperature for the four 
months, 53.5°. 

SuiousY roR Steau-boiler. 
Total coal consumed by steam-boiler from December 23, 1888, to April 
34, 1889, 5 tons 1161 lbs. Average daily temperature for the four months, 

It will be seen by the above that the average temperature of the house 
heated by hot water was 2.3° higher than that heated by steam, and that 
the amount of coal consumed was 2106 lbs. less in the former than in the 
latter. 

[From BaUelin No. 8, April, 1890.] 

Much discussion having been provoked relative to the accuracy of the 
results of experiments with steam and hot water for heating greenhouses, 
reported in Bulletins No. 4 and 6, we h&ve the past winter made a care- 
ful repetition of the experiments to correct any errors that might be found 
and to verify previous results. 

The boilers having been nm with the greatest care possible from 
December i, i88q, to the present date, March 18, 1890, and every precau- 
tion having been taken that no error should occur, we give the results in 
the following table: 





Hot Watkk. 


Steam. 




Letluci and Carnation Room. 


Lettuce and Catnalioa Room. 


Month. 


5 r 


s 


£ 


& K 




^ 


.illi 












S % 










hi 




,■ 1 


<d 


1| 


.11 


Mi^ 


u 




|qh 




■§Sh 


^^^ 


S^ 


¥'■ 


h^ 1 Iqe^ 


r-^ 









" 












Decemtier 

January 

February 

March, 


34.99° 

33-^7 
3^-04 


44-35 
43-67 


57° 
65.96 


47-59° 


1505 

1704 


40.31° 
4J.42 


51-69° 
66.3 = 


46.39° 

49-45 

31.01 


*3So 
3102 
1540 


17 days 


'9-75 


39-94 


5«-«3 




.08s 


39.16 


58... 


46.73 


1692 


Averages 


S'-S'" 


43-37° 


61.06° 


„ 


Total 
6508 


'■■"■ 


So.;8° 


48.39° 


Total 

9784 



SUUHARY FOB HOT-WATER BoiLER. 

Total coal consumed from December i, 1889, to March 1 
lbs. Average daily temperature for the time, 49-74°- 



HEATING AND VENTILATING. 



SmnuRy fjk Steau-boilek. 



Total coal consumed from December i, 1889, to Mardi 18, 1890, 9784 
lbs. Average daily temperature (or the time, 48.39°. 

A saving of fuel in favor of hot vraler of about 33 per cent. 

Similar tests were made under the general directioD of the 
author for the Michigan Experiment Station and are to be 
found reported in full in a paper by the writer, read before the 
American Society of Mechanical Engineers, Volimie XI, For 
this test two houses were used, each of the same size and of the 
same grade of construction. The houses were equally exposed 
to the heat of the sun, but the hot-water house was rather more 
exposed to the wind. The general method of testing was 
essentially the same as that described, and the results show 
substantially the same difference. The heaters used were cast- 
iron of the drop-tube form, quite different from those used in 
' Massachusetts, but well adapted for the work. 

The following table gives a summary of the results: 



SUMMARY OF REStJLTS OF TEST OF HOT WATER AND STEAM. 



Y»T. 


I8B» 


1I90 


M«..h. 


Deeeaber 


J«.u«y. 


PebruuT. 


Much. 


April. 




>D 


J< 


IS 


» 


JO 




i 


ti 


1 


» 


1 


&■ 


i 


fc 


1 


ii 








3> 


'X 


B 


s 




3: 




Tnf 


«« 

n 


M7S 


3799 3400 
90.3 III. 4 


S77S 


S7U 


mHfl 




tSoo 


AveiBgc coal per day . . . : 






fio 


Average outside tempera- 






















,i.» 


^..t 


17.; 


J7.7 »1 




IQ.I 


iO-» 


16. » 


,6 3 


Average outside tempera- 




















ture, 4 P.M 


iB.'i 


18. s 


.»8 


J8 1 ii.l 


„.l 










Average outside tempera- 




















ture, g P.u. . 


l.'!.l 


,lS.i 


17.2 


37..' J7 


27 


3i.e 


K.e 


la 


18 


Average inside tempera- 




















ture. 6 A.ii 


•i^-t. 


H-< 


Si.'i 










^1 ! 


S84 


Average inside lempera- 




















lure, gp.M 


M-'t 


X..1 


S3 t 


S4.8 SJs'sfi 








« .- 


Extreme variation. .. . 


■■ 


U 


4 4j 4 4.3, 4 ^ 






5 9 


A 3 



8CH00LH0USES, SHOPS AND GREENHOUSES. 475 

During the month of April, 1890, the same amount of coal 
was burned in both heaters in order to see what the effect would 
be on the resulting temperature of the two houses. The results 
gave a temperature which averaged 8.5 degrees higher in the 
hot-water-heated house than in the steam-heated house. 

Experiments were made by Prof. L. H. Bailey, of Cornell 
University, in 1891 with houses which were not similar either 
as to exposure or methods of piping, the results of which were 
in general somewhat more favorable to steam than to hot 
water. In 1892 Prof. Bailey arranged the same room so that it 
could be alternately heated with steam and hot water. The 
results of this last test so far as economy is concerned were also 
somewhat in favor of the steam heat. The general conclusions 
which Prof. Bailey drew from this test were as follows: 

Conclusions. 

Under the present conditions the following results can be deduced. 
It will be observed that they confirm several of the conclusions of last 
year. 

1. Hot water maintained a slightly greater average difference between 
the minimum inside and outside night temperature than steam. 

2. There was practically no difference in the coal consumption under 
the two systems. 

3. With a small plant like this the fluctuations under both sy-stems 
are much greater than in larger ones, and neither proved very satisfactory. 

4. The utility of slight pressure in enabling steam to overcome unfavor- 
able conditions is fully demonstrated. 

5. The addition of crooks and angles is decidedly disadvantageous to 
the circulation of hot water and of steam without pressure, but the effect 
is scarcely perceptible with steam under low pressure. 

6. In starting a new fire with cold water, circulation commences with 
hot water sooner than with steam, but it requires a much longer time 
for the water to reach a point where the temperature of the house will 
be materially affected. 

7. The length of pipe to be traversed is a much more important con- 
sideration with water than with steam. 

8. A satisfactory fall toward the boiler is of much greater importance 
with steam than the manner of placing the pipes. 



245. Heating of Workshops and Factories. — ^Workshops or 
factories where counter-shafts and belting are running which 



476 HEATING AND VENTILATING. 

keeps the air in agitation can be heated satisfactorily by erect- 
ing coils of pipe for radiating surface near the ceiling of the 
room. Coils made with branch-tees, as described in Chapter 
VT, may be used, with the pipes placed in a horizontal plane 
and parallel to each other. In such a position the radiating 
surface is very efficient, and the heat given ofif as shown by 
experiment is a maximum. In a coil located near the ceil- 
ing the temperature of the room in the upper portion will 
become very high and will not be evenly distributed unless the 
air k mechanically agitated, so that the overhead system of 
piping is only satisfactory in shops and places where there are 
moving belts or other means for agitating the air. The method 
of proportioning supply-pipes and radiating surface for this 
case has already been considered. Mr. C. J. H. Woodbury 
gives, in Vol. VI, page 86i, " Transactions of American Society 
Mechanical Engineers," considerable useful data relating to 
this method of heating. It is the favorite method for heating 
cotton-mills, about one foot in length of ij-inch pipe being 
used for 90 cubic feet of space. 

246. Summary of Approved Methods for Design of Steam and 
Hot-water Systems of Heating. — ^^For convenience of applica- 
tion the following concise summary of approved methods of 
computation for radiating surface, dimensions of pipes and 
grate surface are here given: 

A. Compute area of windows and outside doors, G, and 
one-fourth the exposed wall surface, \ W, for each room. In 
computing exposed surface estimate ceilings and partitions 
adjacent to unheated rooms as 30 to 50 per cent exposed. 
Denote this result by A . 

B. For direct radiation. Compute 2 per cent of the cubic 
contents of each room. For residence heating take once 
this quantity for second- and third-floor rooms, twice this 
quantity for first-floor rooms, three times this quantity for 
halls; for ofiice, store, or bank rooms, twice this quantity; 
for large assembly rooms, lecture halls, churches, etc., one- 
half this quantity under usual conditions. Denote this result 
by 5. 



SCH00LH0U8ES, SHOPS AND GREENHOUSES. 477 

C. For radiating surfacCy direct heating, multiply the sum 
of the results A and B by one-fourth for steam-heating; multiply 
this last quantity by five-thirds for direct hot-water heating. 

D. For dimensions of piping, direct Jieating, use the tables 
given. The table computed for one-pipe systems of steam- 
heating, commercial sizes of pipes, will apply with accuracy 
for dimensions of pipes for hot-water heating, both return- and 
flow-pipe being of dimensions shown in the table. For two- 
pipe systems of steam-heating use the special table for steam- 
and return-pipes, or use the table referred to above for steam- 
pipes less than 3 inches, taking the main one pipe-size smaller 
than tabulated when above 3 inches in diameter. Take in all 
cases the diameter of return from the special table. 

In applying tables, in all cases, find first the diameter of 
branches to each radiator; second, the diameter of sub-main; 
and third, the diameter of main and return, corresponding 
in each case to total area of radiator and the equivalent length 
of pipe. The equivalent length of pipe is the actual length 
increased by allowance for elbows and bends as explained. 

E. For radiating surjace, indirect heatings multiply the 
result A=G+\W by the following factors for steam-heating: 
for the first floor, by 0.7; for the second floor, by 0.6; for the 
third floor, by 0.5. For hot-water heating multiply each result 
as above by five-thirds. 

F. For dimensions of piping, indirect heating, use the table 
given for one-pipe system of steam-heating, for finding the 
diameter of the steam-pipe in steam-heating and for the 
diameter of flow- and return-pipes in hot-water heating. Take 
the diameter of return-pipe for steam-heating from special table. 
Tables to be used as explained. 

G. Size of air-flues, indirect heating, should be computed 
on the basis of a cross-sectional area for each square foot of 
siurface in the radiator as follows; steam-heating, 1.5 to 2.0 
square inches for the first floor, i.o to 1.25 square inches for the 
second floor, and 0.9 to i.o square inch for the third and 
higher floors. The cold-air flue supplying any radiator should 
have 0.8 the area of cross-section of that of the hot-air flues. 



478 HEATING AND VENTILATING. 

The vent-flues from the room should have an area equal to that 
of the hot-air flues on the first floor, and lo to 20 per cent greater 
for the higher floors. For hot-water indirect heating area of 
flue may be two-thirds as great, reckoned from area (rf radiat- 
ing surface. 

H. Dimensions of register for supplying air should be such 
as to give a net area not less than one and two-thirds to twice 
that of the section of the hot-air flue; for ventilation purposes 
the net area should be 50 per cent greater than cross-sectional 
area of hot-air flue. 

I. To compute heating surface in boiler or heater, divide 
total radiating surface, in which is included the surface of aU 
uncovered pipe, by 6 to 8 for the area of heating surface in a 
steam-heater, and by 10 to 12 for area of heating surface in a 
hot-water heater. 

To compute area of grate divide total radiating surface 
obtained as before by 120 to 200 for steam-heating, and by 
200 to 300 for hot-water heating. 

J. To compute area of smoke-flue first find total radiating 
surface as explained; if for steam, obtain diameter of flue as 
explained in Article 95; if for a hot- water heating system, 
multiply by 0.6 to reduce to equivalent steam-radiation, then 
proceed as before. 



CHAPTER XIX. 
SPECIFICATION PROPOSALS AND BUSINESS SUGGESTIONS. 

247. General Business Methods. — Nearly all heating- 
plants are constructed by contractors, who agree for a specified 
sum to install a heating-plant in accordance with certain speci- 
fications, or, in absence of specifications, one which is guaranteed 
to fulfil certain stipulations as to warming and ventilating in 
any stress of weather. Specifications are prepared either by a 
disinterested third party who is thoroughly familiar with the 
subject, or by the party submitting the proposal. The first 
method, although not conunon except in the case of large 
buildings, is, when the specifications are properly drawn, satis- 
factory both to the owner and the contractor. With proper 
specifications estimates can be obtained from different bidders 
on work of the same class and quantity, and this is likely to 
result in a better quality of work, and often in lower prices. 
Where each contractor bids on his own specifications and 
arranges for apparatus in accordance with his own judgment, 
there will be a very great difference in the quality and method 
of construction proposed, which is likely to result to the advan- 
tage of an unscrupulous bidder, who would, if possible, use 
cheap material and the least possible quantity of heating and 
radiating surface. It is for these reasons to the advantage 
of all concerned that full and complete specifications should be 
provided which will show, accurately, the character, amount 
and quality of the required work. 

The specifications may be written as a part of the tender 
for the work, or as an independent document to which reference 
is made in the proposals. 

The specifications are often accompanied with drawings 

479 



480 HEATING AND VENTILATING. 

which show the location of all the principal parts of the heat- 
ing apparatus and frequently many details of construction; 
the drawings are considered in evety case a portion of the 
specifications and are equally binding on the contractor. 

After the bid has been accepted a contract is drawn which 
should contain a full statement of the agreement between con- 
tractor and owner, and of all conditions relating to the method 
of pajment, penalties, time of completion of work, etc. 

J. J. Blackmore and J. G. Dudley, New York, acting as a 
committee appointed by the National Association of Manu- 
facturers of Heating Apparatus, have given the matter relating 
to uniform specifications much study, and we are indebted to 
them for the following discussion, and also for the copy of the 
uniform proposals here submitted. 

248. General Requirements.*^-" It is not within the scope 
of a work such as this, nor have the trade conditions in the 
heating business advanced to such a point, that all the details 
of any or everj' system can be pro\ided for. The following 
proposed form for uniform standard specifications, however, 
covers the ground as fully as can be done at this time, as is 
shown by the recommendation by the National Association 
of Manufacturers of Heating Apparatus, and if generally 
accepted by heating contractors, manufacturers, architects, 
investors, and the lajmen installing steam or hot-water heat- 
ing apparatus, would result in a higher standard of excellence. 
Much trouble now exists in securing best results, due to 
ignorance on part of owner, architect, or contractor, as weU as 
to unfair competition or unauthorized substitutions of * cheap ' 
materials. 

** Any specification should set forth unequivocally and in 
detail (as far as feasible) all that the contractor is to furnish 
and exactly what is to be accomplished by his guarantee, which 
should embody a standard of economy as well as one of 
etTiciency. The function of the owner or architect is to stipulate 
what results must be accomplished according to standards in 
accepted use, and to give the consulting engineer (when char 

♦Wrillrn for tlii^ work bv ]. J. Hla. kiv.i.n .av! J. (]. Dudley. 



SPECIFICATION PROPOSALS. 481 

acter of heating-plant demands one) or the contractor proper 
latitude as to methods to be pursued. Further than this, it is 
the office of owner or architect, in justice to himself and to 
competing bidders, as well as to the successful contractor, to 
see that the provisions of the specifications are carried out, and 
that the quantity and character of material agreed upon are 
actually furnished and used. Certificates to that end should 
be demanded and given, if it is deemed necessary, since much 
injury is done to a legitimate and beneficial calling by what is 
termed ' skin n ing the job,' that is, agreeing to furnish certain 
things and then by taking advantage of ' lay ' ignorance sub- 
stituting inferior goods or omitting them outright. 

" As already shown, the attainment of certain results follows 
from, and is accomplished by, scientific and mathematical 
processes, whether actually figured and reasoned out, or arrived 
at by ' rule of thumb,' as many really excellent contractors are 
known to do. 

" In illustration, imagine a coimtry residence in course of 
erection after plans by, and under supervision of, a competent 
architect, and note how a proper heating-plant is installed. To 
begin with, the owner should learn from his architect or from 
any other properly informed person that the desired efficiency, 
sufficiency, and results to be procured by the heating system 
depends more on amount of investment than on anything else. 
For instance, the same results can be achieved by employ- 
ing either steam or water. The first cost, however, is less 
with steam, while, it is contended by many, the running and 
ultimate cost is less with water. The reason for this is that 
with the hot-water system as usually installed, with an open 
tank for expansion of water, the temperature of the heating 
medium ranges from 150° to 200° F., while with steam it 
ranges from 212° to 240° F.; as a consequence more radiating 
surface is needed for the former than for the latter. 

" To continue the illustration, let the owner select steam, 
and also suppose that he elects to have indirect heating on 
ground-floor, to obtain extra ventilation (for be it understood 
that some ventilation, accidental or otherwise, is absolutely 



482 HEATING AND VENTILATING. 

necessary to obtain right heating results), while on the upper 
floors he chooses direct heating. This done, it then devolves 
on the engineer, contractor, or architect to determine the 
respective amounts of heating surfaces required to warm the 
several rooms to the indicated temperature according to an 
accepted standard. Much harm at present results from 
demanding and peni\itting the several bidders to estimate on 
different amoimts of heating-surface for exactly the same work. 
The minimum amount should be determined by some one 
individual, who should be recompensed for this service, and he 
alone held responsible for this estimate. The owner or archi- 
tect should indicate on the building plans where surfaces shall 
be placed, bearing in mind always the room required in the 
allotted spaces and also the requirements of the system. This 
is necessary for the contractor to know, since on it depend 
the number of his riser-lines and the amount of piping in his 
boiler-room. 

" When feasible, the owner or architect should indicate all 
the ' specialties ' desired in the apparatus, and each bidder 
should be compelled to figure as nearly as possible on exactly 
the same set of specifications. This method is just to those 
who estimate in good faith, and usually closer and lower figures 
will be obtained by the owner. The contractor, with these data 
before him, takes dimensions either from the architect's plans 
or from the measurements of the building itself; he then com- 
putes the quantity and cost of all materials which will be used 
in the completed apparatus; the method of computation varying 
from that of pure guesswork or shrewd * estimating ' to that 
of painstaking measurement and actual figuring out of the 
exact amount of stock required together with its purchasable 
cost from the trade catalogues and price-lists. 

** To the net cost for material, including boiler, radiators, 
pipe, fittings, valves, vents, floor- and ceiling-plates, registers, 
ducts, covering, painting, bronzing, smoke-pipe, freight and 
cartage, board, car-fares, labor, and incidentals, is added such a 
margin of profit as the contractor considers his experience^ 

kmanship are entitled to. 



SPECIFICATION PROPOSALS. 483 

" In justice to the bidders the conditions of the award 
should be clearly set forth beforehand, and it should be stated 
whether this work will go to the lowest bidder, or whether 
a * preference ' (often justified) is to be given a certain con- 
tractor. When it is known that the preparation of a set of 
specifications and of an estimate of cost is an expense, and 
often not a small one, to each and every bidder, the injustice 
of requiring all to bear this instead of having it done once 
and for all is too evident for argument. It is for this reason 
that a uniform standard specification is recommended by the 
National Association of Manufacturers of Heating Apparatus. 

" Suppose now the award be made to the lowest bidder, 
bids having been made on the same set of specifications which 
embody full statements in regard to requirements of the 
completed plant. The owner (or architect) and the contractor 
are then to execute a proper contract for the performance of 
the work and for the payments therefor. Then each should 
be required to fulfil the conditions of said contract. The 
National Association of Master Steam and Hot-water Fitters 
has adopted a uniform standard contract which seems to meet 
the requirements and is quite generally accepted in such cases. 

249. Form of Uniform Contract. — 

UNIFORM CONTRACT FOR THE CONSTRUCTION OF HEATING 
APPARATUS (TO BE) ADOPTED FOR USE BY THE MASTER 
STEAM AND HOT-WATER FITTERS' ASSOCIATION OF THE 
UNITED STATES.* 

Copyright. 189s, by the Master Steam and Hot-water Fitter's Association of the 

United States.) 

This Agreement, made and concluded at Kalamazoo, 
State of Michigan, the first day of January, in the year one 
thousand eight hundred and Dxatty-five, by and between Jones 
&• Brown, of Chicago, State of Illinois, for themselves and their 
legal representatives, parties of the first part (hereinafter desig- 
nated the Contractor), and R, I. Peters, of Kalamazoo, State 
of Michigan, for himself and his legal representatives, party of 
the second part (hereinafter designated the Owner). 

* Printed words in italics to be supplied in each contract. 



4S4 HEATING ASD \T:STILATISG. 

WrnoissETH. That the Contractor, in conaderatXMi of 
the fulnhnent oi the agreements herein made by the Owner, 
agrees with the said Owner, as follows: 

Article I. The Contractor, tor the coDsideration h«eio- 
after pn>\'ided. covenants and agrees, with the Owner, that the 
Contractor shall and will, within the qiace of Ikree months 
nest, after the date hereof, in a good and wortmaiilike manner, 
and at his own proper char;^ and expense, well and substantially 
build, furnish, and erect a certain Skam Heating .\ppaiatus. at 
444 4ik AztTtuf. City t»f K^jma:M>. according to the Specin- 
catioos. Drawings, and Plans designed by Tkomus Rebimstm. 
ArnkiUit, which Spccincati*xis. Drawings, and Plans are made 
a part of this Contract and are identioed by the signatures of 
the parties hereto. 

.\kiicle n. Xo alteratioos shall be inade in the work 
sliowii or described by the drawings aod speciacations. except 
vp^ya a writien order vM the Arckaects. and when so made, the 
\-ahie oi the wvdt added or ociitCed shill be cooiputed by the 
AKkiiiKts. and the amount so ascerti^oed shaQ be added to os 
deducted trvci the contract price. Is tbe case oi disent from 
scch awird by either f^^^y hen-tv.^. tbe v~.iIuitioa oi the wwt 
aduied or uciittsii shill be reierred t-i zhree 3 dtsraterested 
arbiiraiors. cce to be i?fvtz:"e<i by eich .K toe parties to this 
Coctriot. a^J tie ^^ziL by x^x :w.- thus citoeen: the dedsicxi 
o£ jji> :*■-■ 0: wbi.'c= siill be zcjI isi bcadm^- and each oi the 
port^ btfieto <>■'■"' ^y oce-ajl: o£ the espensis of such 

.\j;r-\:iz III. Shk-tiji ai.y cizsrenof arfee m mtecpretittg 
TJX F'llzs^ jit >peci£oit3.<cs. ia.v-i.'Ci^ii^ or ajscmtEtg additiooal 
o:c:j>;!isi.:ii.'c. tb; Coetnotoc scjil- upuc vritten tkotice itwn 
the v,>irTKC. trcmoiiiteiy eseoire sicc. i=.:ecpc«atixi. the ques- 
CB..<a oE compeseatMt to b« liecemioed oa cx-'mpLetwo. by arbitra- 
tav »} IwlnAel M Aitktt LL 
^jLUa.U IV. .\]: . d wucknxao^t^ of the 

■ <rf tbi. sti«d tn. Skid Spedaca- 

Elf Kserre tbe H^t to 
-t- . ..-: a^ntC. aU matmal or 




SPECIFICATION PROPOSALS. 485 

workmanship of an inferior quality, which said Contractor may 
attempt to use in the erection of said Heating Apparatus, and 
if the said Contractor, after being notified, neglects or refuses 
to do the work, or furnish the materials as called for in the 
Specifications, Drawings, and Plans, then, and in that case, 
said Owner shall give notice in writing to the Contractor, which 
notice is to set forth in full the cause or causes of complaint. 
If the Contractor demurs and refuses to do the work or furnish 
the materials as directed in the notice of complaint, within 
three days from the date of said notice, resort to arbitration 
shall be had as provided in Article II. 

Article V. The Owner shall not, in any manner, be 
answerable or accountable for any loss or damage that shall or 
may happen to the said works, or any parts thereof respectively, 
or for any of the materials or other things used and employed 
in finishing and completing the same, loss or damage by fire 
excepted. The Contractor shall be responsible for all damage 
to the building and adjoining premises, and to individuals, 
caused by himself or his employees in the course of their 
employment. 

Article VI. It is hereby mutually agreed between the 
parties hereto, that the sum to be paid by the Owner to the 
Contractor for said work and materials shall be Seven Thousand 
Dollars {$2,000) , subject to additions and deductions as herein- 
before provided, and that such sum shall be paid in current 
funds by the Owner to the Contractor, in monthly payments, 
to the amount of po per cent of the value of materials delivered 
to and labor performed in the said building during the preced- 
ing month; and the remaining 10 per cent shall be paid as a 
fiinal payment within 50 days after this contract is fulfilled. 

All payments shall be made upon written certificates of the 
Architects to the effect that such payments have become due. 

Article VII. It is mutually agreed that payments for all 
additional work shall be made at the same time and in the 
same manner as contract payments, Article VI. 

Article VIII. It is mutually agreed that should default 
be made in any of the payments as herein provided, the Con- 



486 HEATING AND VENTILATING. 

tractor shall have the right to stop work and withdraw all 
unused materials until such payment is properly made, or may 
at his option cancel the contract. 

Article IX. It is further mutually agreed that the essence 
of this Agreement is that the Owner purchasing this apparatus 
and paying therefor will receive full value to the extent that 
it will warm the subdivisions of the building indicated on the 
plans to JO degrees Fahrenheit in the coldest weather; but 
nothing herein contained, or in the Specification accompanying 
the same, shall prevent the Contractor from receiving from the 
Owner a final payment for the work herein and at the time 
stipulated. 

Article X. The Contractor guarantees his workmanship 
and materials, the capacity of the boiler, the circulation of the 
system and the efficiency of the heating surfaces, all as called 
for in the Specifications hereto attached, and should any defects 
or deficiencies occur, other than from neglect on the part of 
the Owner or his employees, within the term of one year 
from the above date, the Contractor agrees to make good the 
same upon a written notice from the Owner at the Contractor's 
expense. 

Article XI. If at any time there shall be evidence of any 
lein or claim for which, if established, the Owner of the said 
premises might become liable, and which is chargeable to the 
Contractor, the Owner shall have the right to retain out of any 
pajment then due, or thereafter to become due, an amount 
sufficient to completely indemnify himself against such lien or 
claim. Should there prove to be any such claim after all pay- 
ments are made, the Contractor shall refund to the Owner all 
moneys that the latter may be compelled to pay in -discharging 
any lien on said premises made obligatory in consequence of 
the Contractor's default. 

Article XII. It is further mutually agreed, between the 
parties hereto, that no certificate given or payment made under 
this Contract, except the final certificate or final pa>Tnent, 
shall be conclusive e\adence of the performance of this Contract, 
either wholly or in part, and that no partial pajment shall be 



SPECIFICATION PROPOSALS. 487 

construed to be an acceptance of defective work or improper 
materials. 

Article XIII. The said parties for themselves, their 

heirs, executors, administrators, and assigns, do hereby agree 

, to the full performance of the covenants herein contained. 

In Witness Whereof, the parties to these presents have 
hereunto set their hands and seals, the day and year first above 
written. 



In presence of 
/. B. Saxe 



Jones 6* Brown (seal) 

R. J, Peters (seal) 

(seal) 
(seal) 

alternate for article vi. 

It is hereby mutually agreed, between the parties hereto, 
that the sum to be paid by the Owner to the Contractor for 
said work and materials shall be Seven Thousand Dollars {$7,000) 
subject to additions and deductions as hereinbefore provided, and 
that such sum shall be paid in current funds by the Owner to 
the Contractor in installments, as follows: 

When The Boilers are delivered and set, $1,500 

When Steam Mains and Risers are in place, $1,500 
When The Radiators are delivered, $1,500 

When The Radiators are connected, $1,500 

And the balance of $1,000 as a final payment to be made 
within 30 days after this contract is fulfilled. 

All payments shall be made upon written certificates of the 
Architects to the eflfect that such payments have become due. 

250. Duty of the Architect. — The heating system is an 
essential part of the building in this latitude, and it should be 
the duty of the architect to provide building designs of such 
character that it can be readily and economically installed. The 
architect's specifications for the buildings should provide for 
the construction of ventilating, heating, and smoke-flues, and his 



488 HEATING AND VENTILATING. 

plans should show the location, including pipe-lines, of every 
essential part of the heating apparatus. All responsibility 
regarding flues and the general adaptability of the heating sys- 
tem to the building should be assumed by the architect, and 
not shifted to the contractor. If the heating system is designed 
at the same time as the building, slight changes can be made 
in arrangement of details, partitions, doors, etc., that will tend 
to cheapen construction, and will add to the efficiency of opera- 
tion and the general appearance of the heating apparatus. If 
steam- or water-pipes are required to be erected out of sight, 
conduits should be provided, so that they will be readily 
accessible for inspection and repairs. 

251. Methods of Estimating Cost of ConstructioiL — In 
estimating the cost of construction of any system of heating 
apparatus the contractor must depend largely upon his own 
experience and knowledge. No general directions can be given, 
but a few suggestions are offered which may aid in adopting a 
systematic method of proceeding. Determine first the amount 
and character of radiation to be placed in each room by the 
methods which have already been given fully in Chapters X, 
XI, and XII. Second, determine the position and sizes of 
pipes leading from the heater to the various radiating surfaces 
by methods given in Chapters X, XI, and XII. 

To facilitate the above work, a set of floor drawings of each 
story should be obtained, and on these there should be carefully 
laid out the position of all radiators, flues, pipe-lines, etc. After 
determining the amount required, a schedule of material should 
be made and the cost should be computed. 

The manufacturers have adopted a price, which is changed 
very rarely, for all standard fittings, pipes, etc., and from 
which a discount is given which varies with the condition of 
the market, cost of material, labor, etc. The discount is 
usually large upon cast-iron fittings and brass' goods, being 
seldom less than 70 per cent, and sometimes 80 per cent and 
even greater. The discount on piping, especially the smaller 
sizes, is much less, ordinarily ranging from 40 to 70 per cent. 

The cost of labor will vary greatly in different localities, so 



SPECIFICATION PROPOSALS. 489 

that no general method of estimating can be given. It must 
be determined largely by experience in each locality and with 
a given set of men. The cost of heaters of any given type, 
with fittings, etc., can only be determined accurately by cor- 
respondence with manufacturers. 

The list price of the principal standard fittings, together with 
the discount allowed, can be obtained by correspondence, with 
wholesale dealers. 

252. Suggestions for Pipe-fitting. — Certain suggestions are 
here made relating to the actual work of pipe-construction 
which may be useful to those not having an extended experience. 

In the actual construction of steam-heating or hot-water 
heating systems it is usually customary to send a supply of 
pipe and fittings to the building somewhat greater than is 
required, and the workman, after receiving plans of construc- 
tion which show the location and sizes of the various pipes to be 
erected, makes his own measurements, cuts the pipes to the 
proper length in the building, threads them, and proceeds to 
screw them into place. In some rare instances all lengths of 
pipe are purchased the proper length, and the workman has 
merely to put them in the proper position. The skill required 
for pipe-fitting may seem to the novice to be easily acquired; 
this is not true, as it is a trade requiring as much training 
and experience as any with which the writer is familiar. 

The tools belonging to this trade consist of tongs or wrenches 
for screwing the pipe together, cutters for cutting, taps and dies 
for threading the pipe, and vises for holding it in position while 
cutting or threading. A very great variety of tongs and 
wrenches is to be found on the market, some of which are 
adjustable to various sizes of pipe, and others are suited for only 
one size. For rapid work no tool is perhaps superior to the 
plain tongs, and one or more sets especially for the smaller 
sizes of pipes should always be available. . For large pipes, 
chain tongs of some pattern will be found strong and convenient, 
and can be used with little danger of crushing the pipe. A form 
of adjustable wrench known from the inventor as the Stilson 
wrench has proved a very excellent and durable tool, and is 



490 HEATING AND VENTILATING. 

well worthy a place in the chest of any fitter. Other wrenches 
of value are also on the market, one with a triangular head 
and projecting teeth being especially valuable for small pipes. 
The wrenches or tongs which are used for turning the pipe 
in most cases exert more or less lateral pressure, and if too great 
strength is applied at the handles there is a tendency to split 
the pipe. It is an advantage to have the tongs or wrenches 
catch on the outer circumference of the pipe with as little lateral 
pressure as possible, and to this end the projecting edges should 
be kept sharp and clean. 

The cutter ordinarily employed for small pipe consists of 
one or more sharp-edged steel wheels, which are held in an 
adjustable frame, the cutting being performed by applying pres- 
sure and revolving it around the pipe. With this instrument 
the cutting is accomplished by simply crowding the metal to 
one side, and hence burrs of considerable magnitude will be 
formed both on the outside and inside of the pipe. The out- 
side burr must usually be removed by filing before the pipe can 
be threaded. The inside burr forms a great obstruction to the 
flow of steam or water, and should in every case be removed by 
the use of a reamer. Workmen quite often neglect to remove 
the inside burr. A cutter consisting of a cape chisel set in a 
frame is more difficult to use and keep in order, although it 
makes cleaner cuts; it can be had in connection with some 
of the adjustable die-stocks, but is rarely used. Pipes, espe- 
cially the larger sizes, are sometimes cut by expert workmen 
with diamond' pointed or cape chiselSy but this process requires 
too much time to be applicable to small pipes. 

The hack-saw is coming into use to some extent for cutting 
pipes, and is an excellent instrument for this purpose, as it does 
not tend to burr or crush the pipe, and is quite as rapid as the 
wheel-cutter. 

The dies for threading the pipes are of a solid form, each 
die fitting into a stock or holder with handles, or of an adjust- 
able form, the dies being made of chasers, which are held where 
wanted and can be set in various positions by a cam. The 

^ can be run over the pipes several times, and 



SPECIFICATION PROPOSALS. 491 

hence work easier than solid ones; but in their use great care 
should be taken that the exterior diameter of the pipe is not 
made less than the standard size. The cutting edges of the 
dies should be kept very sharp and clean, otherwise perfect 
threads cannot be cut. In the use of the dies some lubricant, 
as oil or grease, kept on the iron will be found to add materi- 
ally to the ease with which the work can be done, and will tend 
to prevent heating and crumbling of the pipe and injury to the 
threads. 

Taps are required for cutting threads in opening or coup- 
lings into which pipes must be screwed — an operation which the 
pipe-fitter seldom has to perform, unless a thread has been 
injured. The vises for holding the pipe should be such as will 
prevent it from turning without crushing it under any circum- 
stances. Adjustable vises with triangular-shaped jaws on which 
teeth are cut are usually employed. 

In the erection of pipe great care should be taken to pre- 
serve the proper pitch and alignment, and the pipes should, 
to appear well, be screwed together until no threads are in 
sight. Every joint should be screwed six to eight complete 
turns for the smaller sizes, 2" and under, and eight to twelve 
turns for the larger sizes, otherwise there will be danger of 
leakage. It is a good plan to test the threads on all pipes 
before erection by unscrewing the coupling and screwing it 
back with the ends reversed. It is also advisable to look 
through each length of pipe and see if it is clear before erect- 
ing in place; serious trouble has been caused by dirt or waste 
in pipes, which would have been removed had this precaution 
been taken. 

In screwing pipes together, red or white lead is often used; 
the writer believes this practice to be generally objectionable, 
and to be of no especial benefit in preventing leaks. The lead 
acts as a lubricant, and consequently aids by reducing the 
force required to turn the pipe. It will generally be found, 
however, that linseed or some good lubricating oil will be 
equally valuable in that respect, and will have the advantage 
of not discoloring the work. 



492 HEATING AND VENTILATING. 

If possible, arrange the work so that it can " be made up " 
with right and left elbows, or right and left couplings. Packed 
joints, especially unions, are objectionable, and likely to leak 
after use. Flange-unions, packed with copper gaskets, should 
be used on heavy work. 

Good workmanship in pipe-fitting is shown by the perfec- 
tion with which small details are executed, and it should be 
remembered that bad workmanship in any of the particulars 
mentioned may defeat the perfect operation of the best-designed 
plant. 

253. Protection from Fire. Hot-air and Steam-heatiiig. — 
Where hot-air stacks or steam-pipes pass up through parti- 
tions near woodwork there is considerable danger of fire, and 
for this reason certain requirements have been made both as 
to the position of hot-air pipes in furnace-heating and steam- 
pipes in steam-heating. The following digest, compiled by 
H. A. Phillips, of the municipal laws relating to hot pipes in 
buildings, in force in some of the principal cities of the United 
States, appeared in the American Architect and Building News, 
Feb., 1893, and is useful in preparing specifications. They are 
as follows: 

Boston. — I. Hot-air pipes shall be at least i inch from woodwork. 

(This may be modified by inspector in first-class buildings.) 

2. Any metal pipe conveying heated air or steam shall be kept i inch from 
any woodwork, unless pipe is protected by soapstone or earthen tube or ring, 
or metal casing. 

Baltimore. — i . Metal flue for hot air may be of one thickness of metal, if built 
into stone or brick wall. 

2. Otherwise it must be double, the two pipes separated by i inch air-space. 

3. Xo woodwork shall be placed against any flue or metal pipe used for con- 
veying hot air. 

Chicago. — I. Hot-air conductors placed within 10 inches of woodwork shall 
be made double, one within the other, with at least § inch air-space between 
the two. 

2. All hot-air flues and appendages shall be made of IC or IX bright tin. 

3. Steam-pipes shall be kept al least 2 inches from woodwork, unless protected 
by soapstone, earthen ring or tube, or rest on iron supports. 

Cincinnati. — Xo pipes conveying heated air or steam shall be placed nearer 
than 6 inches to any unprotected combustible material. .Ml subject to approx'al 
of ins[Hvtor. 

Clr.rlatui. — i. Hot-air conductors placed within 10 inches of woodwork 



SPECIFICATION PROPOSALS. 493 

shall be made double, one within the other, with at least } inch air-space between 
the two. 

2. No pipes conve)ang heated air or steam shall be placed nearer than 6 inches 
to any unprotected combustible material. 

Denver, — ^Metal flue for hot air may be of one thickness of metal, if built into 
Stone or brick wall; otherwise it shall be made double or wrapped in incombustible 
material. 

Detroit, — ^No metal pipe for conveying hot air shall be placed nearer than 3 
inches to any woodwork. Such pipes over 15 feet long shall be safely stayed 
by wire or metal rods. 

District of Columbia, — i. Hot-air pipes shall be at least i inch from woodwork. 

2. Pipes passing through stud or wooden partitions shall be guarded by double 
collar of metal, " giving at least 2 inches air-space, having holes for ventilation, 
or other device equally secure, to be approved by inspector." 

3. Metal pipe double, with the space filled with i inch of non-combustible, 
non-conducting material, or a single pipe surrounded by i inch of plaster of Paris 
or other non-conducting material between pipe and timber. 

Kansas City, — i. Any metal pipe conve)ang heated air or steam shall be 
kept I inch from any woodwork, unless pipe is protected by soapstone or earthen 
tube or ring, or metal casing, or otherwise protected to satisfaction of super- 
intendent. 

2. No wooden flue or air-duct for heating or ventilation shall be placed in 
any building. 

Memphis. — i. All stone or brick hot-air flues and shafts shall be lined with 
tin pipes. 

2. No wooden casing, furring, or lath shall be placed against or over any 
smoke-flue or metal pipe used to convey hot air or steam. 

3. No metal flues or pipes to convey heated air shall be allowed unless 
inclosed with 4 inches thickness of hard, incombustible material, except horizontal 
pipes in stud partitions, which shall be built in the following manner: The pipes 
shall be double, one inside the other, and i inch apart, and with 3 inches space 
between pipe and stud on each side; the inside faces of said stud well lined with 
tin plate, and the outside face with iron lath or slate. Where hot-air pipe passes 
through partition shall be at least 8 feet from furnace. 

4. Horizontal hot-air pipes shall be kept 6 inches below floor-beams or ceil- 
ing. If floor-beams or ceiling are plastered or protected by metal shield, then 
distance shall not be less than 3 inches. 

5. Where hot-air pipes pass through wooden or stud partition, they shall be 
guarded by double collar of metal with 2-inch air-space and holes for ventilation, 
or by 4 inches of brickwork. 

6. No hot-air flues or pipes shall be allowed between any combustible floor 
or ceiling. 

7. Steam-pipe shall not be placed less than 2 inches from woodwork unless 
wood is protected by metal shield, and then distance shall not be less than i inch. 

8. Steam-pipes passing through floors and ceilings or lath-and-plaster parti- 
tions shall be protected by metal tube 2 inches larger in diameter than pipe. 

9. Wooden boxes or casings inclosing steam-pipes and all covers to recesses 
shall be lined with iron or tin plate. 



494 HEATING AND VENTILATING. 

Milwaukee. — i. Hot-air conductors placed within lo inches of woodwork 
shall be made double, one within the other, with at least i inch air-space between 
them. 

2. .Vll hot-air flues and appendages shall be made of IC or DC bright tin. 

Nashvitfe. — i. Sheet-iron flue running' through floor or roof shall have a sheet- 
iron or terra-cotta guard at least 2 inches larger than flue. 

2. Steam-pipes shall be kept at least 2 inches from woodwork. 

3. All steam and hot-air flues and pipes must be suspended by iron brackets. 
Newark. — i. Hot-air pipes shall be set at least 2 inches from woodwork and 

ths woDdA'.)rk protected with tin. 

2. Such pipes placed in lath-and-plaster partitions must be covered with 
iron, tin, or other fire-proof material. 

New York. — (Same regulations as noted under heading of " Memphis.'') 

No hot-air flue or pipe allowed between combustible floor or ceiling. 

Omaka. — i. Steam-pipe shall not be placed less than 2 inches from wood- 
work unless wood is protected by metal shTeld; and then distance shall not be 
less than i inch. 

2. Steam-pipes passing through floors and ceilings, or lath-and-pUster par- 
titions, shall be protected by metal tube 2 inches larger in diameter than 
pipe. 

3. Wooden boxes or casings inclosing steam-pipes and all covers to recesses 
sh ill be lined with iron or tin plate. 

4. Stud partitions in which hot-air pipes are placed to be at least 5 inches 
wide, and the space between studs at least 14 inches. 

5. Hot-air pipes shall not be placed between floor- joists unless same are 
doubled and the joists 14 inches apart. 

6. Bright tin shall be used in construction of all hot-air flues and appendages. 
Providence. — i. Hot-air pipes shall be at least i inch from woodwork, unless 

protected .by soapstone or earthen ring, or metal casing permitting circulation 
of air around pi[>e. 

2. Steam-pipes must be kept at least i inch from woodwork, or supported 
by incombustible tubes or rest on iron supports. 

St. Louis. — I. Hot-air pipes shall be at least i inch from woodwork, unless 
protected by soapstone or earthen ring or metal casing permitting circulation 
of air around pipe. 

2. Steam- or hot -water pipes carried through wooden partition or between 
joists, or in other close proximity to woodwork, shall be inclosed in clay pipe or 
covered with feltinc: or other non-conducting materia!. 

San Francisco. — i. Metal flue for hot air may be of one thickness of metal, 
if built into stone or brick wall; otherwise double, one pipe within the other, 
j inch apart, and space filled with fire-proof materials. 

2. No woodwork shall be placed against any flue or metal pipe used for con- 
veying hot air. 

3. Stcam-pipcs shall l>c placed at least 3 inches from woodwork, or protected 
by ring of soapstone or earthenware. 

]Vi!minii!on. — Metal i)ipes to carr>' hot air shall be double, one inside the 
other. 5 inch apart; or. if single, have a thickness of 2 inches of plaster of Paris 
between pipe and woo<l\vork adjoining same. 



SPECIFICATION PROPOSALS. 495 

254. Heating and Ventilating Laws. — Abstracts of the laws 
relating to the heating and ventilating of schoolhouses and 

public buildings of some of the States, are given here. In a few 

« 

cases regulations by the State board of health are given: 

CONNECTICUT. 

In Revision of the General Statute 1902, Paragraph 2505, under the caption, 
'^ Duties of the State Board," it is stated that " said Board shall take cognizance 
of the interests of health and life among the people of this State; shall make 
sanitary investigations and inquire respecting the causes of disease.'* " Cause 
to be made by the Secretary or by a Committee of the Board of Inspection at 
such times as it may deem best and wherever directed by the Governor or the gen- 
eral assembly of all public hospitals, prisons, asylums or other public institutions 
in regard to the location, drainage, water supply, disposal of excreta, heating and 
ventilation and other circumstances in any way afifecting the health of the 
inmates." 

INDIANA VENTILATION OF SCHOOLHOUSES. 

Approved March 3d, 191 1. 

Section i. That all schoolhouses which shall be constructed or remodeled 
shall be constructed in accordance and conform to the following sanitary 
principles, to wit: 

{B) Building. School buildings, if of brick, shall have a stone foundation, 
or the foundation may be of brick or concrete; provided a layer of slate, stone 
or other impervious material be interposed above the ground line, or the founda- 
tion may be of vitrified brick and the layer of impervious material will not 
be required. 

Every two-story schoolhouse shall have a dry, well-lighted basement imder 
the entire building, said basement to have cement or concrete floor, and ceiling 
to be not less than 10 feet above the floor level. The ground floor of all school- 
houses shall be raised at least 3 feet above the ground level, and have, when 
possible, dry, well-lighted basement under the entire building, and shall have a 
solid foimdation of brick, tile, stone or concrete, and the area between the ground 
and the floor shall be thoroughly ventilated. Each pupil shall be provided with 
not less than 225 cubic feet of space, and the interior walls and ceilings shall 
be either painted, or tinted some neutral color as gray, slate, buff or green. 

(C) Lighting and Heating. All schoolrooms where pupils are seated for 
study shall be lighted from one side only, and the glass area shall not be less than 
one-si:cth of the floor area, and the windows shall extend not less than 4 feet from 
the floor to at least i foot from the ceiling, all windows to be provided with roller 
or adjustable shades of neutral color as blue, gray, slate, buff or green. Desks and 
desk seats shall preferably be adjustable, and at least 20 per cent of all desks and 
seats in each room shall be so placed that the light shall fall over the left shoulders 
of the pupib. For left-handed pupils, desks and seats may be placed so as to 
permit the light to fall over the right shoulder. 



496 HEATING AND VENTILATING. 

(D) Blackboards and Cloakrooms. Blackboards shall be preferably of 
slate, but of whatevei^material, the color shall be a dead black. Cloakrooms 
well lighted, warmed and ventilated, or sanitary lockers, shall be provided for 
each study schoolroom. 

(F) Heating and Ventilating. Ventilating heating stoves, furnaces, and 
heaters of all kinds shall be capable of maintaining a temperature of 70^ F., in 
zero weather and of maintaining a relative humidity of at least 40 per cent; and 
said heaters of all kinds shall take air from outside the building and after heating 
introduce it into the schoolroom at a point not less than 5 nor more than 7 feet 
from the floor, at a minimum rate of 30 cubic feet per minute per pupil, regardless 
of outside atmospheric conditions; ProN-ided, That when direct-indirect steam 
heating is adopted this provision as to height of entrance of hot air shall cot 
apply. Halls, office rooms, laboratories and manual training rooms may have 
direct-steam radiators, but direct-steam heating is forbidden for study scboc^- 
rooms, and direct-indirect steam heating is permitted. 

All schoolrooms shall be provided with ventilating ducts of ample size to with- 
draw the air at least four times every hour, and said ducts and their openings 
shall be on the same side of the room with the hot-air ducts. 

Sec. 2. Whenever, from any cause, the temperature of a schoolroom falls to 
60** F., or below, without the immediate prospect of the proper temperature, 
namely, not less than 70° F., being attained, the teacher shall dismiss the school 
until the fault is corrected. 

ILLINOIS NEW FACTORY \TNTILATION LAW^ 

Senate Bill No. 385 became a law July i, 1909. 

Sec. 2. In every factory, mercantile establishment, mill or workshop, where 
one or more p>ersons are employed, adequate means shall be taken for securing 
and maintaining a reasonable and, as far as possible, equable temperature con- 
sistent with the requirements of the manufacturing process. No imnecessar}' 
humidity which would jeopardize the health of employees shall be permitted. 

NEW VENTILATION LAW IN KANSAS. 

Sec. 4. Ventilation of Theatres and Picture Shows. It shall be unlawful 
for the owner, proprietors or lessee to operate any theatre, picture show or place 
of amusement in any structure, room or place in the State of Kansas which struc- 
ture, room or place is capable of containing fifty or more p>ersons unless the system 
of ventilation is capable of supplying at least 30 cubic feet of fresh air per minute 
for each person therein. 

Sec. 5. Ventilator Fans — Booths for Pictlre MAaiiNES — Electric 
Wirin(.. .-Vll such structures, rooms or places used for the purpose mentioned in 
Section 4 of this act having less than 500 cubic feet of air sp>ace for each person, 
and all rooms having less than 2000 cubic feet of air space for each person in which 
the outside window and door area used for ventilation is less than one-eighth of 
the floor tica, ahall be provided with a draught fan, or other artificial means of 

tt to force the stagnant air outward from said structure, 
oi the room opposite said fan an inlet ventilator shall 



SPECIFICATION PROPOSALS. 497 

be provided of sufficient size to admit the required amount of fresh air as provided 
in Section 4 of this act. All booths used for moving picture machines shall be 
made of galvanized sheet iron of not less than 20 B. W. gauge, or }-inch hard 
asbestos board, securely riveted or bolted to angle iron frame {ot not less than 
iXiXi inch angle iron, properly braced), or equivalent fire-resisting material. 
A not less than 6-inch diameter ventilating-pipe shall be used as an exhaust for 
the hot air generated in operating the machine. AU electric wiring shall be in 
accordance with the National Electrical Code. 

Inspection is to be made at least once ever>'^ six months, and failure to comply 
with the law makes the proprietor, lessee or manager subject to a fine of $10 per 
day for such failure. 

Set of rules by the State Superintendent of Building Inspec- 
tion W. L. A. Johnson, to assist those concerned in fulfilling the 
requirements of the law, as follows: 

" I. With natural ventilation by doors and windows, under normal conditions 
and at normal temperature, the velocity of air travel is estimated to be from 30 
to 60 feet per minute, where the exhaust equals the intake in area. 

" 2. With natural ventilation by ventilating flues and chimneys under normal 
conditions, the velocity of air travel is estimated at 200 to 300 feet per minute. 
The velocity of air travel through ventilators in ceilings will range about 100 
to 150 feet per minute. 

** 3. Small power fans, placed in windows or openings in walls, will give a 
force velocity of air travel from 800 to 900 feet per minute, where the fans com- 
pare reasonably well with the size of the openings. 

" 4. The velocity in number of feet of air travel per minute multiplied by the 
number of square feet of area of openings used for ventilation will give the volume 
of air in cubic feet that will pass through the opening per minute. 

" 5. To determine the required amount of artificial ventilation, multiply 
the number of seating capacity by thirty and from this amount subtract the 
number of cubic feet of air obtained per minute from natural ventilation as 
per rules i and 2. The remainder will be the amount of air in cubic feet to be 
supplied by fans or otherwise." 

One of the things cautioned against in ventilating is the " short circuiting ** 
of air. 

" Baffle " boards for the breakage of drafts also are demanded by the 
law. 

For correct ventilation, the inlet openings should be near the top of the room 
and the outlet near the bottom, and in the opposite end of the room. No intake 
should be placed less than 8 feet above the floor. Where fans are used, it is recom- 
mended that they should all be placed in the outlet, so as to draw the foul air 
from the room. 

The placing of chairs or stools in aisles also is to be tabooed under the new 
law. 

A semi-annual report is required of the fire chief, whose duty it is to inspect 
the buildings to compel whatever change he may desire made. 



498 HEATING AND VENTILATING. 

ABSTRACT OF THE HEALTH LAWS OF STATE OF MAINE, CX)M. 
PILED BY STATE BOARD OF HEALTH, 1909. 

An Act relative to School Buildings. Chapter 88, I^ws of 1909. 

SEcnoN I. It shall be the duty of the State Superintendent of Public Schools 
to procure architects' plans and specifications for not to exceed four-room school 
buildings, and full detail working plans therefor. Said plans and spedficatloDS 
shall be loaned to any superintending school committee or school building com- 
mittee desiring to erect a new school building. For the use of the State Super- 
intendent in procuring such plans and specifications the sum of two hundred dollars 
is hereby appropriated for the year nineteen hundred and nine, and a like sum for 
the year nineteen hundred and ten. 

Sec. 2. Where the plans and ^)ecifications prepared by the State Superintendent 
are not used all superintending school committees of towns in which new school- 
houses are to be erected shall make suitable provision for the heating, lighting and 
ventilating and hygienic conditions of such buildings, and all plans and specifica- 
tions for any such proposed school building shall be submitted to and approved 
by the State Superintendent of Public Schools and the State Board of Health 
before the same shall be accepted by the superintending school committee or 
school building committee of the town in which it is proposed to ere ct such 
building. 

CIRCULAR NO. 65— STATE BOARD OF HEALTH OF M.\INE ON 

BUILDING SCHOOLHOUSES. 

Schoolrooms. — ^The best shape for schoolrooms is th::t of an oblong, the 
vi'idth being to the length about as three to four. The teacher's platform should 
be placed at one end. 

The ceiling should be at least 12 feet high, and if the room is of considerable 
width, especially if unilateral lighting is employed, it may be necessary to ha\'e 
the ceiling somewhat higher. 

In rooms for study it is desirable for each pupil to have 20 square feet of floor 
space, and 240 cubic feet of air space; for example, a room for 35 pupils should 
have 700 square feet of floor surface inclusive of aisles, and should include within 
its walls an aggregate of 8400 cubic feet of air space. \ room 30 feet long, 23 
feet 4 inches ^^ide and 1 2 feet high will fill these requirements. 

Lighting. — The glass surface of the windows should equal at least one-fifth 
of the floor space of the room. 

It is advisable in all school buildings to have double windows. The increased 
cost of construction will be paid by them over and over again in the sa\ing of fuel 
and they facilitate very much that window ventilation which must be the main 
reliance in mild weather. Both sets of sashes should be hung ^ith weights and 
pulleys. 

Heating and Ventilation. — The warming of schoolrooms may be accom- 
plished by usinK stoves, furnaces, or steam heating. 

Direct radiation from stoves or steam-coils should never be used. 

It is practif able to sui)|>ly 2000 r\i\)'u: feel of air \>ct hour for each scholar and 
the plans for ventilation should admit of furnishing this amount at least ordinarily. 



SPECIFICATION PROPOSALS. 499 

Stoves should invariably be jacketed and connected with fresh-air inlets for 
the purpose of supplying fresh air to the room. 

Furnaces should be a kind capable of supplymg 2000 cubic feet of air for each 
scholar hourly, and a capacious fresh-air inlet should never be omitted. 

When steam heating is used the coils should be placed in boxes or fresh-air 
rooms in the basement or elsewhere for the purpose of warming the air before 
it enters the schoolroom. 

School buildings should be so planned as to permit the ducts for fresh air 
and for foul air to be as direct and as free from horizontal extension as possible. 

Inlets and outlets should be of ample size. Their cross-section should equal 
from 16 to 20 square inches at least for each scholar. 

In ordinary schoolrooms it is preferable to place both inlets and outlets on 
the same side of the room, namely, upon the inner or warm side. When so 
placed, the warm air should be admitted 7 feet or more above the floor, and the 
foul air should pass out close to the floor. 

Inlets and outlets should not be constructed with registers which occupy 
much space, but the opening should be covered with stout wire network. 

To insure successful ventilation in all kinds of weather when mechanical 
means are not employed to move the air it is necessary to have means for artifically 
heating the foul-air flue. This may be done by means of an open fire, by a small 
stove set into the base of the shaft, or by steam coils. In small buildings warmed 
with stoves or furnaces, the smoke-pipe of the heater will usually furnish sufiBcient 
heat for this purpose. When thus heated the foul-air flue should contain an iron 
pipe passing up its center, or, in the case of double flues, set in the division wall, 
and into this the smoke-pipe should enter. 

Instead of ventilating by heated flues, the air may be moved by mechanical 
means; that is, by fans run by any available motor. 

Each furnace or steam -heating apparatus should be supplied with a mixing 
valve or other arrangement by means of which warm air and cold air can be 
mixed in such proportions as is required. 

MASSACHUSETTS. 

The following is the Massachusetts State law in regard to 
the ventilation of school and public buildings: 

LAWS ENFORCED BY THE DEPARTMENT OF INSPECTION OF 
THE DISTRICT POLICE, BOSTON, MASS. 

Acts of 1909, Chapter 354. 

An Act to define the powers and duties of the Inspectors of Factories and 
Public Buildings. 

Section i . The Chief of the District Police, the Deputy Chief of the Inspec- 
tion Department of the District Police, and the Inspectors of Factories and Public 
Buildings may, in the i>erformance of their duty in enforcing the laws of the Com- 
monwealth, enter any building, structure or enclosure, or any part thereol, and 



500 HEATING AND VENTILATING. 

examine the methods of prevention of fire, means of exit and means of protectioo 
against accident, and may make investigations as to the employment ol chikircn, 
young persons and women, except concerning health and the influence of occupa- 
tion upon health. 

They may, except in the city of Boston, enter any public building, public 
or private institution, schoolhouse, church, theatre, public hall, place of assemblage 
or place of public resort, and make such investigations and order such structural 
or other changes in said buildings as are necessary relative to the constructioo, 
occupation, heating, ventilating and the sanitary condition and appliances of the 
same. 

Acts of 1909, Ch^ter 514. 

Sanitary, Ventilating and Heating Provisions for Public Buildings and School- 
houses. 

Sec. 105. Ever^' public building and every schoolhouse shall be kept dean 
and free from effluvia arising from any drain, privy or nuisance, shall be pro\'ided 
with a sufficient number of proper water closets, earth closets, or priWes, and 
shall be ventilated in such manner that the air shall not become so impure as to 
be injurious to health. If it appears to an inspector of Factories and Public 
Buildings that further or different sanitation, ventilating or heating provisions 
are required in any public building or schoolhouse, in order to conform to the 
requirements of this section, and that such requirements can be provided without 
unreasonable expense, he may issue a written order to the proper person or authority 
directing such sanitary, ventilating or heating provisions to be provided. A 
school committee, public officer or person who has charge of, or owns, or leases 
any such public building or schoolhouse, who neglects for four weeks to comply 
with the order of such inspector shall be punished by a fine of not more than one 
hundred dollars. Whoever is aggrieved by the order of an inspector, issued as 
herein provided and relating to a public building or schoohouse, may appeal 
to a jud^e of the Superior Court, as provided in chapter four hundred and eighty- 
seven of the acts of the year nineteen hundred and eight. The State Inspectors 
of Health or such other officers as the State Board of Health may from time 
to time app>oint shall make such examinations of school buildings as in the opinion 
of said Board the protection of the pupils may require. The provisions of ttiK 
section may be enforced by the State Inspectors of Factories and Public Buildings. 

FORM NO. 83 A. COMMONWEALTH OF MASSACHUSETTS. DISTRICT 

POLICE— IXSPECTIOX DEPARTMENT. 

In the ventilation of school buildings the many hundred examinations made 
by the insiK'i tors of this department have shown that the following requirements 
can Ik' easily complied with: 

I. That the apparatus will, with proper management, heat all the rooms. 
including: ihc lorridurs. to 70° P.. in any weather. 

That, with the rm^ms at 70 de^Tees and a difference of not less than 40 degrees 
between the lemiKTalure of the outside air and that of the air entering the room 
at the warm-air inlet, the apparatus will supply at least 30 cubic feet of air per 
minute for each scholar accommodated in the rooms. 



SPECIFICATION PROPOSALS. 501 

3. That such supply of air will so circxilate in the rooms that no uncomfortable 
draught will be felt, and that the difference in temperature between any two points 
on the breathing plane in the occupied portion of a room will not exceed 3 
degrees. 

4. That vitiated air in amount equal to the supply from the inlets will be 
removed through the ventiducts. 

5. That the sanitary appliances will be so ventilated that no odors therefrom 
will be perceived in any portion of the building. 

To secure the approval of this dejmrtment of plans showing methods or sjrs- 
tems of heating and ventilation, the above requirements must be guaranteed 
in the specifications accompanying the plans. 

The law requires that a copy of the plans of every public building and every 
schoolhouse (except in the city of Boston) shall be deposited with the Inspector 
of Factories and Public Buildings of the district in which such building is located, 
before the erection of the building is begun, which plans shall also include the system 
or method of ventilation to be provided, together with such portion of the speci- 
fication as the inspector may require. 

The plans usually required are a plan of each floor, including the basement 
and the attic, if the attic is occupied, and a front and a side elevation, and also 
plans and sectional detail drawings of the system of ventilation. Further plans 
may be required by the inspector if deemed by him to be necessary. 

The size of standard classrooms, as generally used in Massachusetts, is 
28X32X 12 feet, and generally seat 48 or 49 pupils. 

MINNESOTA. 

The requirements of the Minnesota State Board of Health, relating to thfi 
construction, etc., of school buildings. 

146. No schoolroom or classroom, except an assembly room, shall have a 
seating capacity that will provide less than 18 square feet of floor space and 216 
cubic feet of air-space per pupil, and no ceiling in buildings hereafter to be erected 
shall be less than 1 2 feet from the floor. 

147. A system of ventilation, in order to be approved by the Minnesota 
State Board of Health, shall furnish not less than 30 cubic feet of air per minute 
for each person that the room will accommodate when the difference of the tem- 
perature between the outside air and the air in the schoolroom shall be 30® F. or 
more. 

148. In a gravity system of ventilation in connection with a furnace or steam- 
plant the flues for admitting fresh air to the room, as well as the vent-flues, shall 
have a horizontal area of not less than i square foot for every nine persons that 
the room will accommodate. 

149. The flues for a plenum or vacuum system of ventilation shall have a 
horizontal area of not less than i square foot for every fifteen persons that the 
room will accommodate. 

150. The window space shall equal one-fifth of the floor space of the school- 
room. 

151. In all rooms not exceeding 25 feet in width all the light shall be admitted 
to the left of the pupils. 



502 HEATING AND VENTILATING. 

152. In rooms exceeding 25 feet in width, light shall be admitted to the left 
and rear of the pupils. 

153. Translucent instead of opaque shades shall be used in the windows for 
controlling the light. 

154. The top of the windows shall be as near the ceiling as the mechanical 
construction of the building will allow. 

155. No cloakroom shall be less than 6 feet wide, nor shall it have less than one 
window. 

156. The so-called " sanitary wardrobe," which allows the foul air of the 
room to pass through the clothing of the children before passing into the vent 
duct, shall be condemned as unsanitary. 

PUfeLIC HEALTH LAWS OF THE STATE OF MONTANA. 

Part III, Title VII, Chapter I, Article I, Revised Codes of 

Montana, 1907. 

Section 1482. Inspection and Regulation of Schoolhouses, Churches 
AND Places of Public Resort: The State Board of Health shall prepare and 
issue to the local and county Boards of Health regulations for the lighting, heating 
and ventilating of schoolhouses, and shall cause sanitar>' inspection to be made 
of schoolhouses, churches and all places of public resort in towns or cities of 1000 
or more inhabitants, and make such regulations concerning the same as it may 
deem necessary for the safety of the persons who may attend school or services 
therein or resort thereto. 

And all schoolhouses, churches or public buildings hereafter erected in such 
towns or cities shall conform to the regulations of the State Board of Health 
in respect to all sanitary conditions; and all persons, corporations or committees 
intending to erect any public building hereinbefore named, in towns or cities 
of 1000 or more inhabitants, shall submit plans thereof, so far as to show the method 
of heating, ventilating, plumbing and sanitary arrangements to the secretary 
of the State Board of Health and secure his approval thereof, or the approval 
of the State Board of Health on appeal from the decision of its secretary, before 
erecting said building, and shall conform strictly to all the requirements of the 
said Board in the respects aforesaid, and any person, corporation or committee 
that shall erect any such building without such approval, and without comply- 
ing with such requirements, shall be guilty of a misdemeanor, and shall also make 
such building conform to the requirements of said Board before the same shall 
be used for any of the purposes above mentioned; and any such use of said 
building until such requirements have been complied with shall be a misdemeanor. 

Sec. 1483. Public Buildings Found in Insanitary CoNDmoN May be 
Declared a Public Nuisance. When any schoolhouse, church, theatre or other 
public building in the State shall, on inspection by a local, county or State health 
officer, be found to b^ in such an insanitary condition as to endanger the health 
of those who may frequent the same, such health officer shall give to the owner, 
or those in charge of such building, notice to place the same in proper sanitary 
condition in such a manner as he shall direct and within a reasonable time, and 
should the owner, agent or other [person in charge of such building fail, IM 



SPECIFICATION PROPOSALS. 503 

or refuse to place the said building in proper sanitary condition, in such a manner 
as shall be directed and within the time specified in said notice, then such build- 
ing shall be deemed a public nuisance, and the local or county health officer or 
the secretary of the State Board of Health shall institute action against the same 
in the manner now provided by law for the abating of a public nuisance. 

The State Board of Health of Montana adopted the following regulations 
for the protection of school children, April i, 1909: 

Regulation 29. Sanitaky Requirements for Schoolhouses. All school- 
houses in towns or cities of 1000 or more inhabitants in the State must conform 
to the following requirements, and it is earnestly recommended that all school- 
houses conform to these requirements: 

Heating. The heating plant must be of such character that the tempera- 
ture of the room or rooms can easily be kept at 70 degrees during the most severe 
weather. 

Lighting. The windows must come to within i foot of the ceiling and the area 
of glass in the windows must be not less than one-sixth of the floor area. All 
windows must be on one side and the rear of the room. No blackboards shall 
be placed between windows. 

Ventilation. The number of pupils seated in a room must be regulated 
so that each child shall have not less than 250 cubic feet of air space. The 
ventilating system must be such that each child will be supplied with not less 
than 1 250 cubic feet of fresh air per hour. When the amoimt of air space provided 
for each child does not exceed 250 cubic feet, the air in the room must be changed 
not less than five times per hour. In buildings of more than four rooms some form 
of forced ventilatiod must be provided. 

Regulation 41. Health Officer Must Inspect Public Buildings. 
Each local or county health officer shall inspect all schoolhouses, churches, theatres 
and other public buildings within his district in towns of 1000 or more inhab- 
itants once in each year, and if any such building is found to be in an insanitary 
condition so as to endanger the health or lives of those who frequent the same, 
or if such building shall fall short of the requirements prescribed by the State 
Board of Health, hereafter to be printed, then such health officer shall take such 
action as is prescribed by law and shall be designated in the regulations of the 
State Board of Health relative to public buildings. 

THE NEW JERSEY LAW CONCERNING PUBLIC SCHOOL BUILDINGS 
—RULES FOR THE APPROVAL OF SCHOOLHOUSE PLANS, 1909. 

Plans of schoolhouses supervised by the business manager. 

AU plans and specifications for the erection, improvement or repair of public 
'schoolhouses shall be drawn by or under the supervision of the business manager, 
if there be one, and shall be approved by the Board of Education. Said business 
manager, if there be one, shall supervise the construction and repair of all school 
buildings and shall report monthly to the Board of Education the progress of 
the work; provided, that repairs not exceeding the sum of $100 may be ordered 
by the committee of the Board having charge of the repair of school property, 
without the previous order of the Board and without advertisement. The 
business manager, if there be one, shall superintend all advertisements for bids 



504 HEATING AND VENTILATING. 

and letting of all contracts. He shall inspect all work done and matrriah or 
supplies furnished under contract, and shall, subject to the approval o£ the 
Board of Education, condemn any work and reject any materiab or supplies 
which, in his judgment, do not conform to the specifications contained in the 
contract therefor, and shall perform such other duties as may be required by the 
Board of Education. 

Approval of Plans by State Board. In order that due care may be eieidsed 
in the heating, lighting, ventilating and other hygienic conditions of public sdiool 
buildings hereafter to be erected, all plans and specification for any such propo s ed 
school buildings shall be submitted to the State Board of Education for suggestion 
and criticism before the same shall be accepted by the Board of Education of the 
district in which it is pro]x>sed to erect such building. 

Requirements in Erecting Schoolhouses. In order that the health, 
sight and comfort of the pupils may be properly protected, all schoolhouses here- 
after erected shall comply with the following conditions: 

Light. Light shall be admitted from the left, or from the left and rear of class- 
rooms, and the total light area must, unless strengthened by the use of reflecting 
lenses, equal at least 20 per centum of floor space. 

Ventilation. Schoolhouses shall have in each classroom at least 18 square 
feet of floor space and ;iot less than 200 cubic feet of air space per pupil. .\11 
school buildings shall have an approved system of ventilation, by means of which 
each classroom shall be supplied with fresh air at the rate of not less than 30 
cubic feet per minute for each pupil. 

Height of Ceilings. All ceilings shall be at least 1 2 feet in height. 

VENTILATION LAW FOR NORTH DAKOTA. 
Act Approved March 6, 19 11. 

'* Section i. No building which is designed to be used, in whole or in part, 
as a public-school building, shall be erected until a copy of the plans thereof has 
been submitted to the State Superintendent of Public Instruction, who for 
the purposes of carrying out the provisions of this act is hereby designated as 
insp>ector of said public-school building plans and specifications, by the persoo 
causing its erection by the architect thereof; such plans shall include the method 
of ventilation provided therefor, and a copy of the specifications therefor. 

*' Sec. 2. Such plans and specifications shall show in detail the ventilation, 
heating and lighting of such building. The State Superintendent of Public 
Instruction shall not approve any plans for the erection of any school building 
or addition thereto unless the same shall provide at least 12 square feet of floor 
space and 200 cubic feet of air space for each pupil to be accommodated in each 
study or recitation room therein. 

** I. Light shall be admitted from the left or from the left and rear of class- 
rooms and the total li^ht area must, unless strengthened by the use of reflecting 
lenses, be equal to at least 20 per rent of the floor space. 

" 2. All ceilings shall be at least 12 feel in height. 

"3. No such i)lans shall be approved by him unless provision is made therein 
for assuring at least 30 cubic feet of pure air every minute per pupil and warmed 



SPECIFICATION PROPOSALS. 505 

to maintain an average temperature of 70** F. during the coldest weather, and the 
facilities for exhausting the foul or vitiated air therein shall be positive and 
independent of atmospheric changes. All schoolhouses for which plans and 
detailed specifications shall be filed and approved, as required by this act, shall 
have all halls, doors, stairways, seats, passageways and aisles and all lighting 
and heating appliances and apparatus arranged to facilitate egress in case of fire 
or accident and to afford the requisite and proper accommodations for public 
protection in such cases. AU exit doors shall open outwardly, and shall, if double 
doors be used, fasten with movable bolts operated simultaneously by one handle 
from the inner face of the door. No staircase shall be constructed with wider 
steps in lieu of a platform, but shall be constructed with straight runs, changes 
in direction being made by platform. No doors shall open immediately upon a 
flight of stairs, but a landing at least the width of the door shall be provided between 
such stairs and such doorway. 

" Sec. 3. No toilet room shall be constructed in any public-school building 
unless same has outside ventilation and windows i>ermitting free access of air 
and light. The provisions of this act shall be enforced by the State Superintendent 
of Public Instruction or some person designated by him for that purpose. 

**Sec. 5. No wooden flue or air duct for heating or ventilating purposes shall 
be placed in any building which is subject to the provisions of this act, and no 
pipe for conve3ing hot air or steam in such building shall be placed or remain 
within I inch of any woodwork, unless protected by suitable guards or casings 
of incombustible material. 

" Sec. 6. To secure the approval of plans showing methods or systems of 
beating and ventilation as provided for in Section 2 the foregoing requirements 
must be guaranteed in the specifications accompanjdng the plans. Hereafter 
erections or constructions of public-school buildings by architect or other person 
who draws plans of specifications or superintends the erection of a public-school 
building, in violation of the provisions of this act, shall be punished by a fine of 
of not less than $100 nor more than $1000." 

NEW YORK STATE VENTILATION LAW. 

An Act to amend the consolidated school law, relative to proper sanitation, 
ventilation and protection from fire of schoolhouses. 

Section i. No schoolhouse shall hereafter be erected in any city of the third 
class or in any incorporated village or school district of this State, and no addition 
to a school building in any such place shall hereafter be erected the cost of which 
shall exceed $500, until the plans and specifications for the same shall have been 
submitted to the Commissioner of Education and his approval endorsed thereon. 
Such plans and specifications shall show in detail the ventilation, heating and 
lighting of such buildings. Such Commissioner of Education shall not approve 
any plans for the erection of any school building or addition thereto unless the 
same shall provide at least 15 square feet of floor space and 200 cubic feet of air 
space for each pupil to be accommodated in each study or recitation room therein, 
and no such plans shall be approved by him unless provision is made therein for 
assuring at least 30 cubic feet of air every minute per pupil, and the facilities for 
exhausting the foul or vitiated air therein shall be positive and independent of 



506 HEATING AND VENTILATING. 

atmospheric changes. No tax voted by a district meeting or other competent 
authority in any such city, village or school district exceeding the sum of $500 
shall be levied by the trustees until the Commissioner of Education shall certify 
that the plans and specifications for the same comply with the provisions of this 
act. All schoolhouses for which plans and detailed statements shall be filed and 
approved, as required by this act, shall have all halls, stairways, seats, passageways 
and aisles and all lighting and heating appliances and apparatus arranged to 
facilitate egress in cases of fire or accident and to afford the requisite and proper 
accommodations for public protection in such cases. All exit doors shall open 
outwardly, and shall, if double doors be used, fasten with movable bolts operated 
simultaneously by one handle from the inner face of the door. No staircase 
shall be constructed with wider steps in lieu of a platform, but shall be constructed 
with straight runs, changes in directions being made by platforms. No doors 
shall open immediately upon a flight of stairs, but a landing at least the width 
of the door shall be provided between such stairs and such doorway. 

Sec. 2. This act shall take effect immediately. 

In a circular issued by the New York State Education Department calling 
attention to the law the following interesting information is found: 

NEW YORK STATE EDUCATION DEPARTMENT, INSPEC- 

TIONS DIVISION. 

It should be noted that the act has been so amended as to require the sub- 
mission of plans for repairing or remodeling school buildings where the cost is in 
excess of $500. 

The following points should be specially observed: 

The plans and specifications must be submitted in duplicate, the original set 
to be returned after the indorsement of approval, the duplicate to be retained 
on file at this Department. The original set is the property of the district and 
in a union free school district should be filed with the clerk of the Board of Educa- 
tion; in a common school district, with the district clerk. 

The plans must show in detail the ventilation, heating and lighting of the 
building. The specifications must contain a statement requiring the contractor 
to guarantee that the system of heat and ventilation described will heat the rooms 
to a temperature of 70 degrees in zero weather and provide at least 30 cubic feet 
of pure air every minute for each pupil to be accommodated in each study or 
classroom. 

At least 15 square feet of floor space and 200 cubic feet of air space for each 
pupil to be accommodated in each study or recitation room must be provided. 
In this connection, il ^ill be necessar>' not only to state the size of the rooms 
(length, breadth and height) but also to give the number of individual desks to be 
placed in the room. 

.Ample cloakrooms should be pro\nded. These should be thoroughly heated 
and ventilated. 

If the closets are located in the basement, the closet for each sex must be 
approached by a separate stairway. The rooms must be well lighted, heated 
and thoroughly ventilated. The ventilation must be entirely independent 01 
the ventilation of the schoolrooms. One seat should be provided for ever>* 25 



SPECIFICATION PROPOSALS. 607 

boys and one for every 15 girls. One urinal should be allowed for every 15 boys. 
Both seats and urinals should be separated into compartments. Absorbent or 
corrosive materials cannot be approved for use in the construction of urinals. 



PENNSYLVAXIA. 
The State of Pennsylvania has the following laws in reference to school buildings: 



SANITARY LAWS RELATING TO SCHOOLS AND SCHOOL 

HOUSES IN PENNSYLVANIA. 

5. Public school buildings to be so constructed that the health, sight and 
comfort of all pupils may be properly protected. Plans for heating, lighting 
and ventilation to be submitted. 

No schoolhouse shall be erected by any board of education or school dbtrict 
in this State, the cost of which shall exceed four thousand ($4,000) dollars, until 
the plans and specifications for the same shall show in detail the proper heating, 
lighting and ventilating of such building. 

6. Light shall be admitted from the left, or from the left and rear of class 
rooms, and the total light area must, unless strengthened by the use of reflecting 
lenses, equal at least 25 per centum of floor space. 

7. Schoolhouses shall have in each classroom at least 15 square feet of floor 
space, and not less than 200 cubic feet of air space per pupil, and for an 
approved system of indirect heating and ventilation, by means of which each 
classroom shall be supplied with fresh air at the rate of not less than 30 cubic 
feet per minute for each pupil, and warmed to maintain an average temperature 
of 70* F. during the coldest weather. 

14. On and after the first day of December, 1907, that it shall be unlawful 
for any board of school directors within this Commonwealth to use a common 
heating stove for the purpose of heating any schoolroom, unless every such stove 
shall be in part enclosed within a shield or jacket, made of galvanized iron or other 
suitable material, and of sufficient height and so placed as to protect all pupils, 
while seated at their desks, from direct rays of heat. 

15. Ventilation: Every schoolroom in this Commonwealth shall be provided 
with ample means of ventilation, and that, when windows are the only means 
in use, they shall be so constructed as to admit of ready adjustment, both at the 
top and bottom, and some device shall be provided to protect pupils from currents 
of cold air. 

16. A thermometer shall be placed in every schoolroom in this Commonwealth 
by the directors in charge, and this provision shall be complied with even when 
standard systems of heating and ventilation are in use. 

17. Penalty: Any school board neglecting or refusing to comply with the 
provisions of this act, may, by proper course of law, be dismissed from office: 
Provided, That when one or more members shall vote to comply with the provisions 
of this act, such member or members shall not be subject to dismissal. 



508 HEATING AND VENTILATING. 

OfflO STATE BUILDING CX)DE. 
Which Became a Law August 14, 191 1. 

TITLE L 
Theatres and Assembly Halls. 

Section 8. Heater Room. Furnaces, hot-water heating boilers and low- 
pressure steam boilers may be located in the buildings, providing the heating 
apparatus, breeching, fuel room and firing room are inclosed in a standard fire- 
proof heater room and all openings into the same are covered by standard self- 
dosing fire-doors. 

No boiler or furnace shall be located under the auditorium, stage, lobby, pas- 
sageways, stairwajrs, or exits of a theatre; or, under any exit, passageway or 
lobby of an assembly hall. No cast-iron boiler carrying more than 10 pounds 
pressure or steel boiler carrying more than 35 pounds pressure shall be located 
within the main walls of any theatre or assembly hall. 

Sec. 16. Automatic Ventilation. The stage, if containing movable scenery, 
shall be provided with one or more ventilators placed near the centre and above 
the highest point of the stage, extending at least six feet above the stage rooi, 
of a combined area equal to at least one-eighth the area of the stage floor. 

The openings in such ventilator shall be closed by valves, louvers or dampers, 
so counterbalanced as to open automatically, and so constructed that ice or 
snow will not interfere with their operation; or, the roof of these ventiUton 
may be made in the form of sliding doors providing all tracks, wheels and work- 
ing apparatus are so placed as to be protected from stK)w and ice. 

All valves, louvers, dampers or doors shall be held closed by hemp or cotton 
cord<%, running to and connecting with the stage floor close to each stage exit door. 
Fusible links shall be inserted in these cords close to each ventilator, ten feet 
above the stage floor and midway between these two points. 

If glass is placed in the ventilator a wire screen of |-inch mesh shall be sus- 
pended under the ventilator and be placed not less than 3 feet below the soifit ci 
the roof. 

Sec. 30. Heating and Ventilation. .\ heating system shall be installed 
which ynW uniformly heat all parts of the building to a temperature of sixty- 
five degrees in zero weather. 

All parlors, retiring, toilet and check rooms, and all assembly halls used in 
connection with and a necessar>' adjunct to a church, school building, lodge bufld- 
ing, club house, hospital or hotel shall be heated by an indirect system combined 
with a s>*stem of ventilation which will change the air not Iras than six times 
per hour. All other assembly halls and theatre auditoriums shall be heated and 
ventilated by a system which will supply to each auditor not less than 1 200 cubic 
feet of air. 

The system to be installed where a chan^ of air is required shall be either 
a gravity or mechanical fumaix system, gravity indirect-steam or hot- water 
qr • merhaniral indirect steam or hot -water system. 

or open grate shall be used in any theatre or assembly hall except 
and boilers. 



SPECIFICATION PROPOSALS. 509 

No stove pipe shall be more than $ feet long, measuring horizontally, unless 
the same be enclosed in a standard fireproof heater room, nor shall any stove 
pipe come closer to any combustible material or ceiling than 3 feet. 

The fresh-air supply shall be taken from outside the building and no vitiated 
air shall be reheated. The vitiated air shall be conducted through flues or 
ducts to and be discharged above the roof of the building. 

No floor register for heating or ventilating shall be placed in any aisle or 
passageway. 

No coil or radiator shall be placed in any aisle or passageway used as an exit, 
but said coils and radiators may be placed in recesses formed in the wall or parti- 
tions providing no part of the radiator or coil projects beyond the wall line. 

PART n. TITLE III. 
School Buildings. 

Section 5. Heater Room. Furnaces, hot-water heating boilers and low-pres- 
sure steam boilers may be located in the buildings, providing the heating apparatus, 
breeching, fuel room and firing room are enclosed in a standard fireproof heater 
room and all openings into the same are covered by standard self-closing fire doors. 

No boiler or furnace shall be located under any lobby, exit, stairway or corridor. 

No cast-iron boiler carrying more than 10 pounds pressure or steel boiler carry- 
ing more than 35 pounds pressure shall be located within the main walls of any 
school building. 

Sec. 7. Dimensions of School and Class Rooms. Floor Space. The mini- 
mum floor space to be allowed per person in school and class rooms shall not be 
less than the following, viz. : 

Primary grades, 16 square feet per person. 

Grammar grades, 18 square feet per person. 

High schools, 20 square feet per person. 

All other schools and class rooms, 24 square feet per person. 

Cubical Contents. The gross cubical contents of each school and class room 
shall be of such a size as to provide for each pupil or person not less than the 
following cubic feet of air space, viz.: 

Primary grades, 200 cubic feet; grammar grades, 225 cubic feet; high schools, 
250 cubic feet, and in grade B buildings, 300 cubic feet. 

Height of Stories. Toilet, play and recreation rooms shall be not less than 
8 feet high in the clear, measuring from the floor to the ceiling line. 

The height of all rooms, except toilet, play and recreation rooms, shall be not 
less than one-half the average width of the rooms, and in no .case less than 10 
feet high. 

Sec. 21. Heating and Ventilation. A heating system shall be installed 
which will imiformly heat all corridors, hallways, play rooms, toilet rooms, 
recreation rooms, assembly rooms, gymnasiums and manual training rooms to a 
uniform temperature of 65 degrees in zero weather; and will imiformly heat all 
other parts of the building to 70 degrees in zero weather. 

Exceptions. Rooms with one or more open sides used for open air or outdoor 
treatment. 



510 HEATING AND VENTILATING. 

The heating system shall be combined with a system of vcntHatidi which 
will change the air in all parts of the building except the corridors, halls and 
storage closets not less than six times per hour. 

The heating system to be installed where a change of air is required shall be 
either standard ventilating stoves, gravity or mechanical furnaces, gravity indirect- 
steam or hot- water; or a mechanical indirect-steam or hot-water S3rstem. 

Where wardrobes are not separated from the class room they sbaJl be considered 
as part of the class room and the vent register shall be placed in the wardrobe. 

If these wardrobes are separated from the class rooms they shall be separately 
heated and ventilated the same as the class rooms. 

The bottom of warm-air registers shall be placed not less than 8 feet above the 
floor line, excepting foot warmers, which may be traced in the floors of the main 
corridors or lobbies. 

Vent registers shall be placed not more than 2 inches above the floor line. 

The fresh-air supply shall be taken from the outside of the building, and no 
vitiated air shall be reheated. The vitiated air shall be conducted through flues 
or ducts and be discharged above the roof of the building. 

A hood shall be placed over each and every stove in the domestic science 
room, over each and e\'ery compartment desk or demonstration table in the chem- 
ical laboratories and chemical laboratory lecture rooms, of such size as to receive 
and carry off all offensive odors, fumes and gases. 

These ducts shall be connected to ventilating flues i^aced in the waDs and shall 
be independent of the room ventilation previously provided for. 

Where electric current is available electric exhaust fans shall be placed in the 
ducts or flues from the stove fixtures in domestic science rooms and chemical 
laboratories, and where electric current is not available and a steam or hot-water 
system is used the main vertical flues from the above ducts shall be provided 
with accelerating coils of proper size to create sufi^ent draft to carry away 
all fumes and offensive odors. 

TITLE X. 
Standard Ventilatinc StoveSw 

Section i. Sto\'E. \ standard ventilating stove may be any st3rle or design 
of heating stove placed within the room to be warmed and ventilated, and shall 
be enclosed in a jacket made of galvanized or black iron. Jacket shall extend 
from the stove tray to a point 4 inches above the top of the stove. 

Sec. 2. Fresh- AIR Supply. Fresh -air supply shall be taken from outside 
the building, be caHed to the stove below the floor line either in vitrified sewer 
pipe, masonry ducts or ducts made of wrought iron or steel, of not less than A 
inch in thickness, riveted together ^^^th tight joints. 

Ducts shall be turned up and discharge under the centre of the stove, from which 
point the air shall ascend between the radiating surface of the stove and jacket 
and enter the nx>m from the top of the stove. 

Sec. 3. Tray. Stovt* shall be placed on a cast-iron tray raised ^ inches above 
the floor line, of the same >ize as the enclosing; jacket, provided with an opening 
of proper size to receive the fre>h-air duct and projecting beyond the stove door 



SPECIFICATION PROPOSALS. 511 

I foot in all directions. Stove door shall be provided with a metal collar extend- 
ing from the face of the stove to the face of the jacket. 

Sec. 4. Smoke Pipe. No smoke pipe connection between the stove and the 
smoke flue shall be more than 5 feet long, measured horizontally. 

Sec. 5. Ventilation. Each room in which a standard ventilating stove is 
installed shall be provided with a ventilating flue placed close to the stove. 

The vent flue shall be of the same area as the fresh-air supply and run through 
and above the roof. Vent flues of not over 150 square inches of area shall be 
enclosed with walls of brick or concrete not less than 4 inches thick, and vent 
flues of a larger area shall be made of brick walls not less than 8 inches thick, 
brick walls 4 inches thick lined with tile flue lining, or monolithic concrete walls 
not less than 4 inches thick. 

Openings to vent flues shall be placed at the floor line, and if vent registeiB are 
used the same shall be 50 per cent larger than the area of the flue. 

SOUTH DAKOTA SCHOOLHOUSE PLANS. 
Teet Legislature of 1907 Passed the Following Law: 

Article XV. Sec. 237. Plans for school buildings approved by State 
Superintendent. 

In order that due care may be exercised in the heating, lighting and ventilat- 
ing of public school buildings hereafter erected, no schoolhouse shall be erected 
by any board of education or school district board in this State until the plans 
and specifications for the same, showing in detail the proper heating, lighting and 
ventilating of such building shall have been approved by the Superintendent of 
Public Instruction. 

Schoolhouses shall have in each class room at least 15 square feet of floor 
space, and not less than 200 cubic feet of air space per pupil, and shall provide 
for an approved system of heating and ventilation by means of which each class 
room shall be supplied with fresh air at the rate of not less than 30 cubic feet per 
minute for each pupil, and have a system of heating capable of maintaining an 
average temperature of 70^ F., during the coldest weather. 

LAWS OF UTAH, 1909. 

Section i. That Section 1823, Compiled Laws of Utah, 1907, be, and the 
same is amended to read as folio wis: 

1823: Plans of New Buildings to be Submitted to Commission. 

Provided that no schoolhouse shall hereafter be erected in any school district 
of this State not included in cities of the first and second class, and no addition 
to a school building in any such place, the cost of which schoolhouse or addition 
thereto shall exceed $1,000, shall hereafter be erected until the plans and specifica- 
tions for the same shall have been submitted to a commission consisting of the 
State Superintendent of Public Instruction, the Secretary of the State Board of 
Health, and an architect to be appointed by the Governor, and their approval 
endorsed thereon. Such plans and specifications shall show in detail the ventila- 



512 HEATING AND VENTILATING. 

tion, heating and lighting of such buildings. The commission herein provided 
shall not approve any plans for the erection of any school building or addition 
thereto unless the same shall provide at least 125 square feet of floor space and 
200 cubic feet of air space for each pupil to be accommodated in each study or 
recitation room therein, and no such plans shall be approved by them unless 
provision is made therein for assuring at least 30 cubic feet of pure air per 
minute for each pupil and the facilities for exhausting the foul or vitiated air 
therein shall be positive and indep>endent of atmospheric changes. No tax voted 
by a district meeting or other competent authority in any such school district 
shall be levied by the trustees until the commission shall certify that the plans 
and specifications for the same comply with the provisions of this act. All 
schoolhouses for which plans and detailed statements shall be filed and approved, 
as required by this act, shall have all halls, doors, stairways, seats, passage- 
ways and aisles, all lighting and heating appliances and apparatus arranged 
to facilitate egress in cases of fire or accident and to afford the requisite and 
proper accommodations for public protection in such cases. 

No schoolhouse shall hereafter be built with the furnace or heating apparatus 
in the basement, or immediately under such building. 

VERMONT VENTILATION LAW. 

Regulations Promulgated by the State Board op Health, Vermont — 
Extracts from Public Statutes of Vermont. 

Reglxations. The following regulations are intended for architects, cor- 
porations, committees or other persons intending to erect any public building: 

I. Plans of each floor, including basement and attic, if the attic is to be occu- 
pied, and front and side elevations, also plans and sectional detail drawings of the 
proposed system of ventilation, plumbing and heating, shall be submitted to 
the local health officer, or State Board of Health. 

The heating and ventilation plans of schoolhouses, hospitals and other public 
buildings shall meet the following requirements: 

(a) The heating apparatus must be of sufficient capacity to warm all rooms to 
70° F., in any weather. 

(6) With the rooms at 70 degrees, and a difference of not less than 40 degrees 
between the temperature of outside air and that of the air entering the room at 
the warm-air inlet, the apparatus must supply at least thirty cubic feet of air 
per minute for each person accommodated in the rooms. 

(f ) Such supply of air should so circulate in the rooms that no uncomfortable 
draft will be felt and that the difference in temperature between any two 
f>oints on the breathing plane in the occupied portion of the room will not exceed 
3 degrees. 

{d) Vitiated air in amount equal to the supply from the inlets should be removed 
through the ventiducts. 

(f) The closets and fixtures must be so arranged and ventilated that no 
odors therefrom will be perceived in any portion of the building. 

To secure the a{)provul of the state or local health olTicials of phins showing 
methods or systems of heating and ventilation, the above requirements must 



SPECIFICATION PROPOSALS. 513 

be guaranteed in the sF>ecifications accompanying the plans. In schoolhouses, 
hospitals and other institutions, the number of occupants intended for each 
room should be given, and in places of assemblage the arrangement of seats and 
aisles should be shown on plans. 

Schoolhouses shall conform to the following detail requirements: 

(a) The site shall be a slight elevation with soil dry and well drained. 

(b) If in a village, it shall be at a point free from noises and unsavory odors. 

(c) If in the rural portion of a town, at a point free from violent winds. 

(d) As near the centre of school population as possible. 

(e) Playgrounds shall be provided for exercise and amusement. 

(/) In villages, or where there is a basement, play rooms can be arranged. 
In rural houses, without basements, a shed should be provided for exercise in 
inclement weather. 

(g) There shall be plenty of pure water supplied for drinking purposes. 

(h) Buildings shall be so located as to secure the best light. Particular atten- 
tion must be given to this in villages where the schoolhouse is likely to be sur- 
rounded by other buildings. 

(0 Care must be taken when the building is of wood to make it warm. This 
can be done either by using thick building paper under the clapboards, or by 
filling the space between the outside boarding and the lath with clean, dry sawdust. 

(j) The walls of the room shall be light grey or buff color. 

(k) All doors shall be hung to swing out, and on large school buildings proper 
fire escapes shall be provided. 

(/) As forty pupils are as large a number as one teacher can well instruct, 
the rooms shall be 32X28X12 feet high, giving from 200 to 300 cubic feet of air 
space and 20 square feet of surface area for each pupil. 

(m) The windows must be numerous, large enough, and so arranged as to 
give ample light to every part (and comer) of the room. The window space should 
be one-fourth of the floor space, and must be not less than one-fifth. There 
must be no more space between the top of the window and the ceiling than is 
required to finish the building, and the window-sill must be 4 feet from the floor 
The light must be arranged so as to fall upon the pupil from the left or left and 
back, never from the front. There must be curtains of a grey or buff color for 
all windows — two to each window — hung in the centre of the window so that either 
the upper or lower half, or both, can be shaded. 

(ft) If there is no cellar under the building, there shall be a space of at least 
2 feet from the floor to the ground, and there shall be windows or openings in the 
underpinning so that there can be a free circulation of air. 

(0) If the corridors are used as coat-rooms they shall be well lighted and 
ventilated. 

Warming and Ventilating Schoolhouses. The heating apparatus must 
be of sufficient capacity to warm all rooms to 70** F. in any weather. 

Not less than 30 cubic feet per minute of pure air for each pupil should be sup- 
plied, and it should be so introduced that there shall be no uncomfortable drafts. 
The difference in temperature between any two ix)ints on the breathing plane 
shall not exceed 3 degrees. The ventilating flues shall be of sufficient size to readily 
introduce and remove the requisite amount of air from the room. 

In rural houses of one room where a furnace is impracticable, the above con- 



514 HEATING AND VENTILATING. 

ditions can most economicaUy and satisfactorily be met by the use of the *' iack- 
eted stove," as shown. The ordinary wood-buroer box stove may be surrounded 
by a casing, or jacket, of galvanized iron, with proper air space of 6 to 9 inches 
between jacket and stove. Fresh air should be conveyed from the outside of build- 
ing through tin tube to space under stove. 

The vent or foul air pipe (also of tin) should be set on legs with an opening 
at the bottom, 12 inches from the floor, to run straight up through the roof as high 
as the chimney. The stove-pipe should enter this at not more than 6 feet from 
the floor, passing up as far as possible before it leaves the vent pipe for cfainmey. 
There should be a door in the jacket at the rear end of the stove whidi can be 
opened for pupils to warm their feet. 

State Board of Health. 
September 20, 1909. 

VIRGINIA. 

Chapter 187: An Act for the Purpose of Regulating the Constructiosi 
OF PuBuc School Buildings in Order that the Health, Sight and 
Comfort of all Pupils May be Properly Protected. 

Approved March ii, 1908. 

1. Be it enacted by the General Assembly of Virginia, that the State Board 
of Inspectors for public school buildings shall not approve any plans for the erec- 
tion of any school building or room in addition thereto unless the same shall 
provide at least 15 square feet of floor space and 200 cubic feet of air space for each 
pupil to be accommodated in each study or recitation room therein, and no such 
plans shall be approved by said board unless provision b made therein for assuring 
at least 30 cubic feet of pure air every minute per pupil, and the facilities for 
exhausting the foul and \ntiated air therein shall be positive and independent of 
atmospheric changes. All ceilings shall be at least 1 2 feet in height. 

2. All schoolhouses for which plans and detailed statements shall be filed 
and approved by said board, as required by law, shall have all halls, doors, stair- 
ways, seats, passageways and aisles, and ail lighting and heating appliances 
and apparatus arranged to facilitate egress in cases of fire or accidents, and to 
afford the requisite and proper accommodations for public protection in such 
cases. All e.xit doors in any school house of two or more stories in height shall 
open outwardly. Xo staircase shall be constructed except with straight runs. 
changes in direction being made by platforms. Xo doors shall open immediately 
upon a flight of stairs, but a landing at least the width of the doors shall be pro- 
vided Ix'twecn such stairs and such doorways. 

3. All schoolhouses, as aforesaid, shall provide for the admission of light 
from the left, or from the left and rear of the pupils and the total light area must 
be at least 25 per centum of the floor space. 



CHAPTER XX 
AIR CONDITIONING 

255. Air Conditioning is the art of positively producing and 
controlling any desired atmospheric conditions within an 
enclosure with respect to moisture content, temperature and 
purity. The purity has reference to the dust carried by the 
air as well as poisonous and noxious gases. The principle 
object, however, is the regulation of moisture or the humidity. 

256. Useful Results of Air Conditioning. — In many indus- 
tries, such as the manufacture of textiles, food products, high 
explosives, photographic films, tobacco, etc., the artificial regu- 
lation of atmospheric moisture or humidity and the removal 
of the dust and some of the gaseous impurities of the air is 
of the greatest importance. 

When applied to the blast furnace, it has increased the 
net profit in the production of pig iron from $0.50 to $0.70 
per ton, and in the textile mill it has increased the output 
from 5 to 15 per cent, at the same time greatly improving 
the quality of the product and also the hygienic conditions 
surrounding the operatives. In many other industries, such 
as lithographing, the manufacture of candy, bread, high explo- 
sives and photographic films, and the drying and preparing 
of delicate hygroscopic materials such as macaroni and tobacco, 
the question of hiunidity is equally important. 

257. Percentage of Humidity Desirable. — From a physio- 
logical standpoint this subject is of importance. Messrs. 
H. W. Clarke and Stephen De M. Gage in a paper read before 
the Health Association, Washington, D. C, 191 2, say,* "The 
feeling of depression felt in badly ventilated rooms is largely 

* American Journal of Public Health, Nov. 1913. 

515 



516 HEATING AND VENTILATING, 

caused, not by excess of carbonic acid or depletion of the air 
of oxygen or by toxic substances emitted from the occupants, 
but from the fact that the temperature and humidity have 
increased, and normal evaporation from the skin has been 
reduced, thereby affecting the temperature regulating mechan- 
ism of the body and the entire nervous and circulating s>*stems. 
According to Haldane and others, it is the sensible tempera- 
ture, or that indicated by the wet bulb thermometer, which 
the body feels, and the actual or dry bulb temperature and 
the real humidity, are of minor importance under ordinary' 
conditions. With a wet bulb temperature above 88° F. in still 
air, heat stroke is likely to occur even with persons wearing 
little or no clothing and doing no work, while in the case of 
persons dressed in ordinary clothing and doing muscular work, 
serious effects may follow at ver\- much less sensible tempera- 
ture. On the other hand, eminent phj-sidans assert that 
excessively dr\' air is harmful, causing a thickening of the mucous 
membranes and aggravation of catarrhal conditions. What 
degree of humidity is most conducive to the comfort of indoor 
workers is an open question and undoubtedly depends somewhat 
upon the nature cf the emplojTnent. There is little question, 
however, that the comfort, and probably the health, of persons 
employed in the majority of textile processes is affected to a 
greater or less extent, as the wet bulb temperature of the air 
measures above 70" to 75^ F." 

As a result of a thorough test of three months duration 
in the Oliver Wendell Holmes School in Boston bv Charles 
F. Eocleth and Dr. T. W. Harrington, the following conclusions 
were deduced : 

First. To secure the greatest comfort, the relative humidity 
should not exceed 55 per cent; somewhere between 45 and 
50 per cent is probably the best range. 

Seayfid. With the humidity at 55 per cent, the temper- 
ature of the room should never rise above 65 ' F. A tempera- 
ture of from 61" to 62* F. will give better results. 

Third, Moistening the air up to 40 per cent or above 
should not be attempted, unless both the heating system and 



AIR CONDITIONING. 517 

the humidifying apparatus can be kept under close control. 
With a room temperature of from 70° to 75° and a relative 
humidity of 50 per cent, there is a very pronounced feeling 
of oppression and physical discomfort as well as a per- 
ceptibly disagreeable odor. If temperature rises above 75^, 
the relative humidity should not rise above 35 per cent. 

258. Humidity and its Determination.* — The conditions 
of the atmosphere as regards moisture involves two distinct 
elements: (i) The amount or weight of vapor present, which 
is called absolute hiunidity, and (2) the ratio of this to the 
amount which would produce saturation at the existing tem- 
perature, which is called relative humidity. The sensation of 
relative dryness or moisture depends chiefly upon the second 
of these elements. 

Water has the property of emitting vapor in a confined 
space at a definite pressure or tension, depending upon its 
temperature whether the space is filled with air or not. If 
the vapor is sufficient to fill a given space, the space is satu- 
rated and the maximum vapor tension is produced; with 
insufficient vapor a less vapor tension is produced. The 
amount or weight of moisture present would be the same 
whether the space is a vacuiun or whether it is filled with 
air or any other gas. Contrary to the usual opinion, air has 
no capacity for absorbing moisture. By lowering the tem- 
perature sufficiently, the vapor contained in a confined space 
may be condensed and may appear as dew. The exact tem- 
perature at which the formation of dew ceases, with rising 
temperature, is called the dew point. The relative humidity, 
scientifically, is the ratio of vapor tensions at the dew 
point and at the actual temperatures. It may be calculated 
from the values given in standard vapor or steam tables. 
An abbreviated table of the properties of saturated vapor 
in a confined space follows. This table gives the tension and 
weight per cubic foot for the dew point temperature, found 
as explained later. Thus, supposing that the actual tem- 
perature is 60° F., and the dew point temperature is 50° 

* For definitions of humidity, dew-point, etc., see Sec. 28, p. 36. 



518 



HEATING AND VENTILATING. 



F., the weight of vapor would be given in column 4 correspond- 
ing to 50°, which is 0.00059 pound per cubic foot. This vapor 
weight or absolute hiunidity would remain constant if the 
temperature in the confined space were increased, but the rela- 
tive hiunidity would be diminished, because the vapor present 
is not sufficient to produce saturation or dew point at a 
higher temperature. The table shows that at 60° F. the 
weight of vapor at saturation is 0.00083 pound per cubic 
foot. The relative humidity is the ratio of the tensions at the 
dew point and at the observed temperatures, or, for the 
example selected, the tension at 50 degrees, 0.363, divided 
by the tension at 60 degrees, 0.522, is 0.696. The tension 
due to the vapor is always the same at the same temperature 
whether the confined space is occupied by air or not, but the 
total pressure in the confined space is the sum of the vapor 



TABLE OF VAPOR TENSIONS, DENSITY AND LATENT HEAT AT 

SATURATION OR DEW-POINT 



1 


2 


3 


4 


5 


Temp. Fahr. 


Pressure or Tension. 


Density or 
Weight. 


Latent Heat. 


Degrees. 


Lbs. per Sq.in. 


Inches of Hg. 

• 


Lbs. per Cu.ft. 


B. T. U: per Lb. 
Vap^T. 


32 


0.089 


0.180 


0.00030 


1073 


35 


1. 100 


0.203 


0.00034 


1072 


40 


0.122 


0.248 


0.0041 


1069 


45 


0.148 


0.300 


0.00049 


1066 


SO 


0.178 


0.363 


0.00059 


1063 


55 


0.214 


0.436 


0.00070 


1061 


60 


0.256 


0.522 


0.00083 


1058 


65 


0.305 


0.622 


0.00098 


loss 


70 


0.362 


0.739 


0.00115 


1052 


75 


0.429 


0.873 


0.00135 


1050 


80 


0.505 


1.029 


0.00157, 


1047 


85 


0.594 


1.209 


0.00183 


1044 


90 


0.696 


1-417 


0.00213 


1041 


95 


0.813 


1.655 


0.00247 


1038 


100 


0.946 


■ 1.926 


0.00285 


1036 


105 


1.098 


2.236 


0.00328 


1033 


no 


I. 271 


2.589 


0.00377 


I04S 


115 


1.467 


2.438 


0,00431 


1027 


120 


1.689 


3 987 


0.00492 


X024 



AIR CONDITIONING. 519 

pressure and that already existing in the space. Thus, if 
the air in a confined space were at a pressure of 29.18 inches 
of mercury and the temperature at dew point were 70 degrees, 
there would be an additional vapor pressure at dew point 
of about 0.74 inches, making a total pressure of 29.92 
inches Hg. 

Coliunn No. 5 in the table gives the heat required to vapor- 
ize one pound of water, or condense one pound of vapor at 
the given temperature. Thus to condense one pound of vapor 
at 60° F. there must be absorbed 1058 B. T. U.; conversely, 
to evaporate one pound of water from and at 60° F., there will 
be required an expenditure in heat of 1058 B. T. U. If a change 
of temperature occurred without any evaporation or conden- 
sation, the heat interchange would be calculated by multi- 
plying the range of temperature by the weights and specific 
heat of each constitutent element and finding the sum of 
the products. 

Dew-point Determination, — One of the most common and 
best known instruments for determining the dew-point is 
Danieirs hygrometer, which consists of a bent tube with 
a hollow globe or bulb at each end and partly filled with 
ether. The lower bulb is of black glass and contains a ther- 
mometer, while the upper bulb is wrapped with muslin. The 
instrument is supported by a stand which carries a thermometer 
for giving the atmospheric temperature. It is used by passing 
the liquid to the lower bulb and then moistening the upper 
or covered bulb with ether. The evaporation on the surface 
of the covered bulb causes a drop in temperature and con- 
sequently condenses part of the vapor within it. This produces 
an evaporation in the lower bulb and a lowering of the tem- 
perature. When moisture first appears on the lower bulb 
the temperature is noted, then the instnmient is allowed to 
stand until the moisture disappears, when the temperature 
is again read. The mean of these temperature readings is 
the dew-point. The dew-point hygrometer is inconvenient for 
the determination of the relative hiunidity and is not used 
as extensively as the wet and dry bulb thermometer or sling 



520 HEATING AND VENTILATING. 

psychrometer described on page 37, which mvolves a different 
principle and does not give the dew-point. The wet and 
dry bulb instrument with proper handling and the use of 
accurate tables or charts gives the relative humidity as accurately 
as desired for practical purposes. 

259. Dust. — Ordinary air always contains a greater or 
less amount of both dead and living matters in suspension, 
which may have an important influence upon the health. 
The dead matter of the dust consists of particles of mineral 
matter from the streets and pavements and from vehicles 
and machinery, and the organic matter from the floors and 
walls, from clothing, and from the emanations of men and 
animals. Dust, when present in excessive amounts, irritates the 
mucous membranes of the lungs and respiratory passages and 
renders them more susceptible to invasion by the germs of dis- 
ease. The living matter consists of bacteria, yeasts and molds 
which are always present in greater or less numbers, and which 
have found their way into the air from the emanations from 
animal and vegetable life. So far as is known the yeasts and 
molds have little pathological significance, but it is well recog- 
nized that the germs of tuberculosis, pneumonia, influenza and 
perhaps other diseases are frequently transmitted through 
the air. 

The presence of dust in the atmosphere allows the con- 
densation to take place whenever the air is cooled to the sat- 
uration point, whereas if there were no dust, condensation 
would require a much lower temperature. Many of the dust 
particles in the air are extremely minute; each one serves, 
however, as a nucleus for water-vapor to condense on, and 
is rendered visible by placing the air under examination in an 
air-tight receiver saturated with water vapor. The particles 
may be counted on a micrometer by expanding the air with 
an air pump and producing condensation if the number of 
particles are less than 500 per cubic centimeter. If the 
number of particles exceed that amount, the air is diluted 
with knovm volumes of air free from dust until the number 
is less thftr ' cubic centimeter. The number of dilutions 



AIR CONDITIONING. 521 

multiplied by the number counted serves to give the niunber 
of dust particles. 

The weight of dust is sometimes obtained by forcing known 
volumes through a filter or body of water and determining the 
dust by finding the increase of weight. 

The dust particles are greatly reduced by increasing the 
relative humidity, thus when the wet bulb depression is 2° 
to 4°, the number of particles are less than one-half those 
found when the wet bulb depression is 7°. They are almost 
entirely removed by washing. 

It is rare to find any air containing less than 100 particles 
of dust per cubic centimeter, and in cities the numbers may 
be as high as 100,000 to 150,000 per cubic centimeter. Even 
over the ocean the nimiber usually exceeds 300 per cubic 
centimeter. 

260. Solubility of Gases. — The water employed in air wash- 
ing net only absorbs the solid dust particles but it absorbs 
many of the gaseous impurities, so that such water is likely 
to be charged with dangerous impurities.* 

The following table gives the number of volumes of certain 
gases that one volume of water will dissolve at 68° F. tem- 
perature and a pressure of 29.98 inches of mercury. 

Ammonia, NHr- 710.00 

Carbon dioxide, CO2 0.00072 

Carbon monoxide, CO 0.023 

Chlorine, CI o. 226 

Hydrogen, H 0.017 

Hydrogen sulphuric, H2S 2.91 

Nitrogen, N 0.0158 

Oxygen, O o . 03 

Nitrous oxide, N2O o. 67 

Methane, CH4 oo35 

Ethylene, C2H4 0.15 

Acetylene, C2H2 103 . o 

Sulphur dioxide, SO2 0384 

♦ Paper by Prof. G. C. Whipple, Am. Public Health Association, 1913. 



522 HEATING AND VENTILATING. 

261. Combustibility of Gases. — Smells and fumes are often 
compbsed largely of complex hydrocarbons which are prac- 
tically insoluble in water, but are combustible when passed 
through fire, where they are decomposed into water and carbon 
dioxide, etc. This can often be done by installing exhaust 
fans and ducts to take the contaminated air to the ash pits 
of boiler or of other furnaces. Wherever practical, any indus- 
trial process producing noxious fumes should be equipped 
with an adequate system of hoods, discharging into chimneys, 
or induced draft fans conveying them to places where they are 
rendered harmless by proper treatment. 

Poisonous gases, such as carbon monoxide, which are heavier 
than air, should be prevented from settling into unventilated 
cellars or pits in which such gases may collect. 

262. Regulation of Relative Humidity.* — This operation will 
require the addition of vapor, or humidifying, when humidity 
is to be increased, and the reduction of vapor, or dehumidify- 
ing, when it is to be decreased. As has been pointed out, an 
increase in temperature will decrease the relative humidity, 
and a decrease in temperature will increase the relative humidity. 

In some industries, such as textile mill work, the necessity 
for some means of increasing the relative humidity has long 
been realized and met by crude means without much regard 
to the health or comfort of the operatives. 

Old methods of humidifying : 

(a) Sprinkling the floor, or " degging " as it is called; 

(6) the use of shallow channels in the floor or shallow pans 
for water; 

{c) Introductions of steam into the room usually through 
deep cans to prevent dirty water and oil from injuring 
the goods. 

Modern methods of humidifying : 

Hiunidifiers may be classified into Spray and Evaporative 
types, and the latter again divided into direct and indirect. 

♦ See papers by W. H. Carrier and Frank L. Busey, read before the A. S. M. E. 
in 191 1, and entitled "Rational Psychrometic Formulae ' ancd "Air Conditioning 
Apparatus." 



AIR CONDITIONING. 523 

The relative humidity of air may also be increased by the 
direct introduction of steam into the air supply, or into the 
room. This method raises the temperature perceptibly and 
is therefore intolerable in most cases. It is also objectionable 
because it introduces a noticeable odor so that its use is of 
little engineering interest. 

For ventilation purposes both the spray and the evap- 
orative types of humidifier have an additional value, due to 
the cooling efifect, which is in direct proportion to the moistening 
effect. The direct spray type is distinguished from the evap- 
orative type in that it introduces a finely divided or atomized 
spray directly into the room in constant volume, while the 
evaporative type introduces only a water vapor. 

There is also a mixed type which discharges both moist 
air and free moisture into the room. 

In what may be termed the indirect evaporative humidifier 
the air is partly or entirely taken from the outside and humidified 
and conditioned before it is introduced into the room. This 
system is also called the central system. In the direct evap- . 
orative type the water vapor passes directly into the air of 
the room. The direct spray type of himiidifier introduces a 
fixed quantity of moisture into the room regardless of the 
condition of the room until it is closed off by hand, or by an 
automatic control. 

In the automatic type there is an inherent self-regulating 
feature, owing to the fact that the rate of evaporation is in 
direct proportion to the deficiency in moisture in the air. This 
is especially true in the indirect evaporative type, which, with 
all conditions of outside air, may be made to maintain an 
absolutely uniform relative humidity, other conditions remain- 
ing constant. 

The essential features of a modern humidifier are as follows: 

a. A diffuser which serves as an eliminator to prevent 
water from being carried outward against the air current. 

b. A system of atomizing sprays so arranged as to fill the 
air completely with water particles uniformly distributed over 
iht chamber area. 



524 HEATING AND VENTILATING. 

c. A centrifugal pump for maintaining the proper pressure 
on the spray nozzles. 

d. A settUng chamber provided with proper strainers for 
the removal of dirt from the spray water. 

e. An eliminator for washing the air by impact and cen- 
trifugal force and for the removal of all free moisture. 

/. An automatic water heater for suppljdng heat and moisture 
to the air through the water spray. This may be either of the 
closed type or of the open, ejector type. 

g. A dew-point thermostat subject to the temperature of 
saturation and connected to motor valves controlling the 
supply of heat to the spray water. 

Air is drawn through this hiunidifier at a velocity of about 
500 feet per minute. The temperature of the air is raised 
immediately in the hiunidifier from out-door temperature, to 
that necessary to hold the desired amount of moisture. 

263. Automatic Humidity Control. — There are three dif- 
ferent methods by which such control can be secured: (a) by 
two separate thermostats, one of which is placed at the himiid- 
ifier just beyond the eliminator plates. This controls the 
temperature of the dew-point by an automatically operating 
valve or damper governing the means of operating the tem- 
perature of the spray water, of the entering air or of both in 
conjunction. The other thermostat placed in the room main- 
tains a constant room temperature, either by controlling the 
temperature of the air entering the room or by controlling 
some source of heat within the room. With these two tem- 
peratures maintained constant the percentage of humidity in 
the room will remain constant and will depend upon the dif- 
ference between the dew-point temperature maintained at the 
humidifier and the temperature maintained in the room. 

(6) By a differential thermostat: This t>pe of dew-point 
control is required wherever it is impracticable to maintain 
either a constant dew-point or a constant room temperatiu^. 
In this method there are two elements, one of which is exposed 
to the dew-point ^ «hile the other is exposed to 

the room t^ ^nnected that they act 



AIR CONDITIONING. 525 

conjointly upon a single thermostatic valve connected with 
operating motors arranged to control the dew-point temperature 
in relation to a variable room temperature, or to control the 
room temperature with respect to a variable dew-point tem- 
perature. 

(c) By means of some form of differential hygrostat which 
controls the wet bulb temperature with respect to the dry bulb 
temperature so as to maintain a constant relative humidity 
with regard to the dew-point for variation in room temperature. 

264. Relatiye Humidityi Variation.* — ^The degree of satura- 
tion of the air leaving any type of air washer depends upon 
the intimacy of the contact of the air and water, and upon the 
relation of the water temperature to the wet bulb tempera- 
ture of the entering air. It also depends to some degree upon 
the length of the spray chamber as well as upon the velocity 
of the air passing through it. With the centrifugal type of 
spray nozzles the water pressure is a most important element 
affecting the degree of saturation. 

Tests made on a standard humidifier having four ^inch 
orifice centrifugal spray nozzles per square foot, and the wet 
bulb depression of the entering air maintained constant at 
16® F., showed that an increase of 2| pounds (from 25 to 
27.5 pounds) per square inch permitted an increase in the 
air velocity up to 670 feet per minute through the spray 
chamber with perfect saturation of the air, while with 25 
pounds pressure and a velocity of 500 feet per minute the air 
was not perfectly saturated. This effect was undoubtedly due 
to the increase in fineness of the spray rather than to the 
increase in the amount of water discharged. The water was 
discharged in the opposite direction from the air flow. 

When the spray water is recirculated without heating as 
in warm weather, it remains at all times substantially at the 
wet-bulb temperature of the entering air, while the wet-bulb 
temperature of the air leaving the washer or humidifier is 
■trachanged. Therefore it follows, in conformance with the 
V that when the air is completely saturated as in the 

*•*« by Carrier and Bussey, Transactions A. S. M. E., 191 1. 



526 HEATING AND VENTILATING. 

humidifier the air is cooled to the wet-bxUb temperature of the 
incoming air. This cooling effect is due to the transformation 
of sensible heat into latent heat of evaporation and is there- 
fore in direct proportion to the moisture added to the air. 
The wet-bulb depression in atmospheric air averages from 12 
to 15 degrees in siunmer, while occasionally a depression of 
20 to 30 degrees is found in extremely hot and dry weather. 
In every case the humidifier will cool the incoming air a cor- 
respondmg number of degrees. 

When saturation is incomplete, as in the ordinary air 
washer, the wet-bulb depression of the air leaving the washer 
is foimd to be a constant percentage of the initial wet-bulb 
depression, when the air velocity remains constant. 

It also follows that the cooling effect is a constant per- 
centage of the initial wet-bulb depression. This may be ex- 
pressed by the formulae 



^' ^? = i-i?=£, (2) 



h-t' 



where 



/' = constant wet-bulb temperature; 
/i = temperature of air entering washer; 
/2 = temperature of air leaving washer; 
/? = constant ratio depending upon intimacy of con- 
tact, air velocity, etc.; 
i—R = E = efficiency of saturation. 

265. Power Required for Operating Humidifiers. — The fol- 
lowing table * gives the power required to saturate 1000 cubic 
feet of air per minute at various velocity conditions, based on 
overcoming the resistance of the humidifier, using a fan with 
a static efficiency of 45 per cent, which is a fair value. 

* See paper by Carrier and Bussey, A. S. M. E. Transactions, 191 1. 



AIH CONDITIONING. 



527 



TABLE n. RESISTANCE OF HUMIDIFIERS AND HORSE-POWER 
REQUIRED TO HUMIDIFY 1000 CUBIC FEET OF AIR. 



Velocity 

through 

Spray 

Chamber in 

Ft. per Min. 


Assumed 

Resistance 

in Inches of 

Water. 


Resistance 

in Oz. per 

Square Inch. 


350 


O.II3 


. 0647 


400 


0.147 


0.0850 


4S0 . 


0.186 


0.1075 


500 


0.239 


0.1323 


SSO 


0.277 


0.1600 


600 


0.330 


0.1906 


650 


0.387 


0.2240 


700 


0.450 


. 2600 


750 


0.516 


0.2990 



Horse-power to 

Move 1000 Cu. 

Ft. Air per 

Min. at 45 

Per Cent Fan 

Efficiency. 



0.0391 
0.0513 
0.0652 
o . 0800 
0968 
1 150 
1350 
1570 
1810 



Horsepower for 

Spray per 1000 

Cu. Ft. of Air 

(A Orifice 

Nozzle). 



0.1408 
0.1231 
0.1095 
0.0985 
o . 0897 
0.0822 
0.0758 
0.0704 
0.0658 



Total Horse- 
power 
Required 
per 1000 
Cu. Ft. 
of Air. 



0.1799 
0.1744 
0.1747 
0.1785 
0.1865 
o. 1972 
0.2108 
0.2274 
o . 2468 



This does not include the power required to overcome 
the resistance of the ducts, which varies considerably, but 
should not exceed that required for the humidifier. The 
resistance of the heating * coils is not considered, because in 
summer when the largest supply of air is usually required the 
air is by-passed aroimd the heaters while in winter the require- 
ments are so much smaller that the total horsepower is greatly 
reduced and the total resistance is but slightly increased. 
The power required to pimip the water is based on the use 
of centrifugal pumps having an efficiency of 55 per cent and 
using ^-inch orifice nozzle with rotary self-cleaning strainers. 
266. The Relation of Cooling Effect to Percentage of Rela- 
tive Humidity.* — In the moist air system of humidifying it is 
essential that the difference between the dew-point tempera- 
ture of the incoming air and the room temperature shall not 
exceed a predetermined value, depending upon the percentage 
of humidity to be maintained. The minimum temperature at 
■which air can be introduced is the dew-point or saturation 
temperature at the apparatus. This permissible temperature 
rise limits the possible cooling effect to be obtained from each 
:rubic foot of air. The proper relationship of these factors 
s of primary importance in the design of humidifying systems. 

In the majority of industrial applications the problem 
Glaring warm weather, and in some instances throughout the 

* See paper by Carrier and Bussey, A.S.M.E. Transactions, 191 1. 



528 HEATING AND VENTILATING. 

entire year, is as much a question of cooling as of humidifying. 
In the moist air system one is dependant upon the other. In 
every air conditioning plant there are four sources of heat 
which must be taken into account in the design of the system. 

a. Radiation from the outside owing to the maintainence 
of a lower temperature inside. At ordinary hiunidities this 
is negligible, but at high humidities and in dehumidifying 
plants it is an important factor, owing to the increased tem- 
perature difference. This may be calculated from the usual 
constants of radiation. 

b. The heating effect of direct sunlight. This is especially 
noticeable from window shades and exposed windows and 
skylights where the entire heat energy of the sunlight is ad- 
mitted to the room, and from the roof, which constitutes the 
greater amount of sunlight exposure, and which in the ordinar>' 
construction transmits heat much more readily than the walls. 
Precautions should be taken where high hiunidities are desired 
to shade exposed windows and to insulate the roof thoroughly. 
Ventilators in the roof are of great advantage in removing 
the hot layer of air next it and those of ample capacity should 
always be provided. 

c. The radiation of heat from the bodies of the operatives. 
This amounts to about 400 to 500 B. T. U. per operative, 
about one-half of which is sensible heat, the other half being 
transformed into latent heat through evaporation. 

d. The heat developed by power consimied in driving the 
machinery and in the manufacturing processes in general. 
According to the laws of conservation of energy, all power 
used in manufacturing is ultimately converted entirely into 
its heat equivalent. Each horsepower of energy therefore 
creates 42^ B. T. U. of heat per minute which must be cared 
for by ventilation. In high-powered mills this is the chief 
source of heating and is frequently suflScient to overheat the 
building even in zero weather, thus requiring cooling by ven- 
tilation the year round. 

Relation of room temperature to outside wet-bulb tem- 
perature: During cold weather the dew-point or saturation 



AIR CONDITIONING. *VJ*J 

temperature at the apparatus is sccurcil and controUinl arti- 
ficially at whatever point required. During warm weathiT, 
however, it is impossible, during the greater i>art of i\\v tinte, 
to obtain as low a dew-point as desired withiuit rrfrigrratitm. 
The lowest saturation temperature that can he obtained (whrre 
the water is refrigerated) is the same as the outside wet bulb 
temperature; therefore the dew-point in the room will always 
be the same as the outside wet-bulb temperature. The dilTerenre 
between the dew-point and room temperatures is <lependt*nl 
upon the relative humidity maintained so that the highrr the 
humidity the lower the room temperature may be kept,. 

267. Dehumidifier. — May be of the spray type or of tlir 
surface t>pe. A knowledge of the relation of walrr ti-niprr 
ature to the discharge air temperature in either tyjie is tr?>s4*nliiil. 
In the spray tjT)e of one stage having two banks of op|xir»i'd 
nozzles, the air temperature leaving is practically idcntiial 
with the temperature of the leaving water; the difLtrenn; 
never exceeds one degree in proi>erIy designed apparatu:). 
The air will always be saturated when leaving, and undrr 
some conditions there is a slight tendency Ui entraininenl 
even after thorough elimination. 

The degree of entrainment will dej^irnd ui>';n tfjc rnnin: of Uiin- 
f)erature of both the air and the water. In g^m^rral tjj<: hiualhtr 
the temf)erature range the greater the Ur/id'rii' y i.-, lo f/joi.^ture 
entrainment or supKrrsaturation. Thib JTiay f/«; n:*i .'jA. wliere 
a considerable lowering of air teiTii^eratun; i-. r*.'\AnA., by 
pasang the ziir succeb:?f ully through two or /;-or«: \, .r/iidiik-rs 
IE series. When the *} sterr- ii ijToi/^r]y *i*^A'/jiK*\ th«; cfjtrauii- 
Tiie::t sboJd ziA bt vJL*A^::A, to t^x^ the true dew-jy^int Ueu^- 
j»era:ure :r.:rt th^- orit cfr^rre*;. 

Tzxt Sv-ri*. wzjt dti -"rilLLer :: <lM»; Vy or;:./ Uw: air i.» 
?u'o5lLi:U£.ll-. :hc bjjr.*: •.rr- :yrri_ •.,.'*: <.*, ^Jll*; ...vr<:\ water. MSbi'- 

IL lilt SUriLlc :*.~»t liitTr: 1: -t^ ... . ; 'Vr: ; ' \0 2 ' '>«Xn>l;i:><lil]«l(SUt 

JL ::»:»iii:r vii:. irit rinv •/.-^ \^'.'jV'*, -. '".»r-^l«:.fi well 



S30 



■ HEATING AND VENTILATING. 



tern, this higher water temperature permits a much increased 
ammonia pressure in the water cooler, often doubling the 
absolute pressure. As shown in the following table, this in- 
creases the capacity of the ammonia pressure corre^iondingly 
and accordingly reduces the horse-power required per ton of 
refrigeration. The ammonia condenser of course remains 
unchanged. 

TABLE in. B.T.O. REFRIGERATION REQUIRED TO COOL 1000 CUBIC 
FEET OP .MR (MEASURED AT 70 DEGREES) FROM A GIVES 
WETBULB TEMPERATURE TO A GIVES DEW-POIXT. 



t 

u 




BnUiiBC Wtt-bolb T«np=™toit 


1! 


s» 




«o i 6i 


! 


Ss 


»» 4i 
ss ; JS 




l»S 


S 


MS o 6SJ S 

t>ll O tDt.O 


ig6 , M6 941 
I [6s 14T* lijo 


i 



'I 



2<i8. R«frigen(ioo Reqnind for Ddumudifyiiig- — The heat 
to be remo>~ed in cooling a known wdght of air fn»n a gi\'en 
temperature and moisture content to a given dew-point tesn- 
pemture b eWdently the difference of the total heat quantities 
contaiaed in the air under these respecti^'e coDditi(»ts. The 
total sA the Utent and specitic heats in one pound of pure air 
is dependent upon the wet-bulb temperature onl>-. Tabic 5 
$ho«'$ the amount ot refrigeration required to cool and defau- 
midify toco cubic teet of air between \~arious gneo wet-bulb 
temperatures and doal dew-pi.iiats. The amount of water 
re^iuired to cool air in i one-#tajce spray sj-stem dehumirfitJer 
may be calcuUced from the foregoing data as foQows. 






J/- ■ 



III 



AIR CONDITIONING. 531 

whence 

jr= weight of water in pounds; 
iV= weight of air in pounds; 
^= initial water temperature; 
/i' = initial wet-bulb temperature of air; 
^2 = final dew-point temperature of air; 
Hi = initial total heat in i pound of air at wet-bulb tem- 
perature, /'; 
H2 = total heat in i pound of air at final dew-point, /2 ; 

--|r = approxmiate rate of total heat change at the given 

temperature per degree change in wet-bulb temper- 
ature, t'\ 

To find the final temperature possible with a given weight 
of water and of air at temperature, ^ and /i', respectively, 
we have from (i) 

WU-'Wh^NW—fNh^ (3) 

Hence 

NW—,-Wt, 

269. Air Washers. — ^Air washers differ from humidifiers prin- 
cipally in the object to be accomplished. In the humidifiers 
the main object is to bring the air to the proper relative humidity 
and temperature. In the air washer the chief aim is to obtain 
pure air free from all foreign substances such as poisonous 
gases, noxious odors, dust and bacteria. In the open coimtry 
nature provides for purifying the air through the agency of 
rain. Alfred E. Stacy, Jr., in a paper before the A. S. H. & V. 
Engineers, states that " a heavy rain acts as an air washer and 
removes from the air all but traces of dust. This has been 
proven conclusively by daily readings taken on the roof of 
I the Chicago City Hall.'' In cities, however, dust from the 
streets, smoke, germs and impurities from the bodies of the 



532 HEATING AND VENTILATING. 

inhabitants, are in such abundance as to require further atten- 
tion than nature can provide. With natural ventilation all 
the dust is carried into the buildings through the open windows 
and this is especially true of the lower stories of the buildings. 
With artificial ventilation the supply of air is usually taken 
near the ground, and unless some means of purification is em- 
ployed the dust from the streets is forced into the rooms of 
the building to be breathed by the occupants and to settle 
upon the furniture and decorations, causing rapid deterioration. 
The essential parts of a modern air washer are: a spray cham- 
ber, an eliminator and a sump or tank. Other accessories 
necessary to the operation, where the washing water is re-cir- 
culated, are: a pump, a strainer, and some motive power for 
driving the piunp. The spray in the spray chamber does 
not need to be so finely divided as in the case of a humidifier 
for industrial purposes, where the air must be completely 
saturated, and the spray may be directed with the current 
of air. A coarser spray also probably has a better washing 
effect than the very fine spray, and the power required to 
produce the very fine spray is greater. In cold weather, tem- 
pering coils are also necessary, since the temperature of the 
spray watet would become too cold and the relative himaidity 
in the building would become abnormally low. In warm 
weather the washer will have but slight cooUng effect, which 
will be proportional to the increase in relative humidity, except 
where cooling coils are used or where fresh cold water is supplied 
for the spray. 

In cases where the amount of air required for heating is 
substantially in excess of that required for ventilation, as is 
probably the case with a large class of buildings, the practice 
of re-circulating part of the air through the air washer would • 
result in a considerable saving of heat. However, the use 
of direct radiation to supply the heat in excess of that carried 
by the air neccesary for ventilation would be more economical 
and would obviate the danger of re-circulating too much of 
the air and thereby imparing the ventilation. 



APPENDIX 

CONTAINING 

REFERENCES AND TABLES. 



LITERATURE AND REFERENCES. 

The literature devoted to the subject of warming and ven- 
tilation is quite extensive, dating back to a treatise on the 
economy of fuel and management of heat by Buchanan in 
1 815. A most excellent compilation of this literature was 
made by Hugh J. Barron of New York, in a paper presented to 
the American Society of Heating and Ventilating Engineers at 
its first meeting in January, 1895, from which the following 
list of books has been copied : 

A Treatise on the Economy of Fuel and Management of Heat. Robert- 
son Buchanan, C.E. Glasgow, 181 5. 

Conducting of Air by Forced Ventilation. Marquis de Chahannes. 
London, 18 18. 

The Principles of Warming and Ventilating Public Buildings, Dwell- 
ing-houses, etc. Thos. Tredgold, C.E. London, 1824. 

Warming, Ventilation, and Sound. W. S. Inman. London, 1836. 

The Principles of Warming and Ventilating, by Thos. Tredgold, with 
an appendix. T. Bramah, C.E. London, 1836. 

Heating by the Perkins System. C. J. Richardson. London, 1840. 

Illustrations of the Theory and Practice of Ventilation, with Remarks 
on Wanning. David Boswell Reid, M.D. London, 1844. 

A Practical Treatise on Warming by Hot Water. Chas. Hood, F.R.S. 
London, 1844. 

History and Art of Warming and Ventilating. Walter Beman, C.E. 
London, 1845. 

Warming and Ventilation. Chas. Tomlinson. London, 1844. 

Walker's Hints on Ventilation. London, 1845. 

Practical Treatise on Ventilation. Morrill Wyman. Boston, 1846. 

533 



534 HEATING AND VENTILATING. 

Trait£ de la Cbaleur. E. P£clet. Paris. Fiist edition, 1848; second 
edition, 3 vols, 1859. 

Practical Method of Ventilating Buildings, with aji appendix on Hat- 
ing by Steam and Water. Dr. Luther \'. BeU, Boston. 1848. 

Warming and Ventilation. Cbas. Tomlinson. London, 1850. 

Practical \'entilatian. Robert Scott Bums. Edinburgh. 18501 

Ventilation and Warming. Henry Ruttan. New York, 1862. 

A Treatise on Ventilation. Robert Richey. London. 1862. 

American edition of Dr. Reid's Ventilation as Applied to American 
Houses, edited by Dr. Harris. New York. 1864. 

A Treatise on Ventilation. Lewis W. Leeds. Philadelphia. 1S68; 
New York, 1871. 

Observations on the Construction of Healthy Dwellings. Capt. 
Douglas Gallon. Oxford. 1875. 

Practical Ventilating and Warming. Jos. Constantine. London. 1875. 

Wanning and Ventilation. Chas. Tomhnson, London, i8;6. Sixth 
edition. 

Mechanics of Ventilating. Geo. W. Rafter, C.E. New York, 1878. 

Ventilation- H. A. Gouge. New York. 1881. 

Ventilation. R. S. Bums. Edinburgh. i83i. 

American Practice in Wanning Buildings by Steam- Robert Briggs- 
Edited by A. R. Wolf, with additions. Xew York, 1881. 

Steam-heating for BuQdings. W. J. Baldwin. Xew York. t88j- 
Thirteenth edition published in 1893. 

The Principles of \'entil3tion and Heating. John S. Billings, M.D. 
New York, 1884. 

Heating by Hot Water. Walter Jones. London. 1884. 

A Manual of Heating and \'entiIa(ion. F. Schumaii. Xew Vorii, 1886- 

Venlilation. W. Butler. Edited by Greenleaf. Xew York, 1888. 

Steam-heating Problems from the Saniiarj- Engineer. Xew York, 18&I. 

Metal Worker Essays on House Heating. Xew VoHl, iSgo. 

Heat — Its Application to ihe Warming and Ventilation of Buitdings. 
John H. Mills. Boston. iSyo. 

Ventilation and Heating. T. Edwards. London. 1S90. 

Ventilation— -A Text-book to the .An of Ventilating Building Wm. 
Paton Buchan. London, i8gi. 

Tbe Ventilating and Warming of Scbod Building Gilbert B. Mor- 
rison. New Yoik, 1893. 

Hoiwji« Hcuiag. Wm. J. Baidwin. New Votk. i.fgj. 

VeDtikiion uml HfUig ^^ Jnftnt A BJUtep. M.D. New York, 1 

Wuming by HOt^b^mBtS/tt^lS- £<iit«d by F. Dye. Lnn- 
iJon, i8w- «^^^^^^^^^^^ 

Healing ud W^^^^^^^^^^^S"^' ^^ ^"'''' '^^- 
Fiist edtlion. 



. APPENDIX. 535 

Furnace Heating. Wm. G. Snow. New York, 1902. 

Schoolhouse Heating and Ventilating. Joseph A. Moon. Boston, 

1905. 

Ventilation and Heating of Dwellings. J. W. Thomas. London, 1906. 

Heating and Ventilating Notes. John R. Allen. Chicago, 191 1. 
Third edition. 

Principles of Heating. Wm. G. Snow. New York, 191 2. 

Mechanics of Heating and Ventilation. Konrad Meier. New York, 
1912. 

Handbook of Heating and Ventilation. J. D. Hoffman. New York, 
191 2. Second edition. 

Heating and Ventilating. R. C. Carpenter. New York, 191 5. Sixth 
edition. 

CURRENT LITERATURE OF THE DAY 

The current literature relating to this subject is extensive, 
and consists mainly of magazines and papers published weekly 
or monthly. In these journals are to be foimd from time to 
time descriptions of new apparatus and complete drawings of 
plants recently constructed which will prove invaluable in the 
study of this art. 

The American Society of Heating and Ventilating Engineers, 
formed soon after the publication of the first edition of this 
book, has contributed greatly to advance the scientific and 
practical knowledge of the art of heating and ventilating. 
Much information for the sixth edition of the work has been 
obtained from the Transactions of the Society, which are the 
most valuable books of reference yet published for heating and 
ventilating engineers. 

EXPLANATION OF TABLES 

Of the tables which have been given a few only need special 
explanation in order to fully understand their use. These are 
as follows: Table No. VII, Logarithms of Numbers. This table 
will be found of very great convenience in facilitating any 
operation involving multiplication and division. Thus it will 
be found in every case that the sum of two logarithms is the 
logarithm of a number equal to the product of the two num- 
bers whose sum was taken, and the difference of two logarithms 



536 HEATING AND VENTl^LATING. 

is the logarithm of the quotient obtained by dividing one by 
the other. Every logarithm consists of two parts: a decimal 
part, which is given in the table, and an index or characteristic, 
which must be prefixed. The index or characteristic is a whole 
nimiber and is one less than the nimiber of integral places; 
for a decimal number it is negative and one more than the 
number of ciphers between the decimal point and the first 
significant figure. Thus, to find the logarithm of 254, a number 
containing 3 integral places, the index is 2, the decimal part of 
this logarithm found opposite 25 and under 4 in the table is 
4048, making the full logarithm 2.4048. If the number had 
been 25.4 the index would have been i, the decimal part as 
before. If the number had been 0.0254, the index would have 
been minus 2, the decimal part the same as before. 

As an illustration showing how to multiply by logarithms, 
multiply 254 by 2.48. We have: 

The logarithm of 254 =2.4048 

2.48=0.3945 



( ( it tt 



Log. of product = 2.7993 

The sum of these two logarithms, which is the logarithm of 
the product, is equal to 2.7993. The index, or number 2, is of 
use in showing that there are three figures or integral places in 
the result. To find the logarithm, look in the table for the 
number next smaller than 7993; in this case the result is exact 
and is found opposite 63 in the column marked zero, indicating 
that the product is 630; the actual product of these numbers 
is slightly less than this, the difference, however, being scarcely 
ever of any practical importance. Had our number been 7994, 
it would have been one greater than 7993 and 6 less than the 
logarithm of the next number. In that case our number would 
have been 630 1, which, reduced to a decimal, would have been 
the number to consider as the product. The logarithm of a 
power can be found by multiplying the logarithm by the nimi- 
ber which represents the power and the logarithm of a root by 
dividing by the index of the root. 



APPENDIX. 637 

Thus, to raise 368 to the fifth power, we have: 

Log. 368= 2.5658 

Multiply by 5 

Log. 5th power = 12.8290 
No. = 674j expanded to 13 places = 6745000000000. 
To extract the 5 th root of 368: — 

Log. 368 = 2.5658 
Divide by 5 =0.51316 = log. of root 
Root =3.259 

In general the table will be found to aflford an easy methocj 
of dividing or multiplying, and it will be well worth while to 
become master of its use. 

The table which is printed in the book is correct for 4 places 
of figures only, but tables of 7 and even 13 places have been 
printed. 

The four-place table can be used with confidence for all 
operations not requiring extreme accuracy. It will in almost 
every case be found suflSciently accurate for all practical prob- 
lems of designing. 

The method of using Table No. XII to determine the 
amount of moisture in the air has been quite fully explained 
in Chapter II. The method of using Table No. XIII (prop- 
erties of saturated steam) has been fully explained in Chapter 
VIII. The reader should note that the steam-pressure tabulated 
is that above a vacuum, and not the reading of a pressure-gauge. 
The pressure-gauge reads from the atmosphere, which is gen- 
erally 14.7 pounds above zero; hence, in order to use the table 
add 14.7 pounds to the steam-gauge reading for the pressure 
above zero. The other quantities will be quite readily under- 
stood. 

The table for equalization of pipe areas has been quite fully 
explained in Chapter XV. The number of pipes of the size, as 
shown in the side column, required to give an equivalent area 
to the one in the top column is given by the numbers. Thus 
14.7 pipes I inch in diameter have a carrying capacity equiva- 
loit to th^t n{ one xme 3 inches in diameter. 



538 



HEATING AND VENTILATING. 



SQ 
< 



PC 

< 

O 



< 
'A 





Bushelt 
to Hecto- 
litres. 


ro t* O ^ »>• •-> vao « 
00*-iMk«e«e«firo 




Cu. Yds. 

to Cubic 

Metres. 


»0 0* -f « r»j t* <t O »- 
»>-w><i ooo lOf^ — ao 


• 

o 


O •-• « i^'O'^iOOOl 


Cu. Ft. 
to Cubic 
Metres. 


roo 0> <t lO Oi W »0« . 
OCO -l"0- ^OC<C T 
n tO90 « ^O ^ •^ i/J 

d d d d d d o d d 




Cu. Ins. 
to Cubic 
Centi- 
metres. 


t* ^« O'C f^ O r^ n' ' 
«- fonox » - -^ ^ 

»« »« »M ■ 






1 1 1 1 1 b B M H . 
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•* 5 > 2 



Acres to 
Hectares. 


^ 0* ^X «*>« W t* N 


1 

t 
1 

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1 


OO*-iMe«<i<iM}r0 


Sq. Yds. 

to Sq. 

Square 

Mctfes. 


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fO t^ O tX « lOX PI 

XOw>*^«-i OXOi'l 


O •-• <i "O ^««««0 r^ 


Sq. Ft. 
to Sq. 
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I 


Sq. Ins. 
to Sq. 
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W •») lO t*X O »- "^ »« 
^» -ox fl t»«o o 

O <i 0>tO(<«XV)MX 


i 

1 


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1 1 1 1 1 1 B 1 1 

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APPENDIX. 



539 



o 

CQ 



m O 

•2S^42 



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V3 •»« 




US=S 



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M M M N n r« r«) 



u I 



2.i 



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COO 



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n H n H II H II II II 






3 



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w <i •^^»'>0 1^00 Oi 






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f*5 t^ O "t* •-■ •'500 P* 
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oocoooooo 

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ii .< « C« f>1 «>») f*) 




II II II II II II II II II 
w c« fo n ifi>0 t*x c 





Grams 

to 
Ounces 
Troy. 


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pt fO n~0 t^ O O « »*! 
« •fooo O f^^t^O- 
<^0 9 n O Oi M lox 
OOO'^'^ — '^'tN 




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MiUiers or 

Tonnes 

to Pounds 

Av. 


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nO<*5M f^r*<iO ►- 
00«-'>-'N<^'^'*jn 
« to 00 O w to « 
w tOX •- '*jiOi'> O 




Quintals 
to 
Pounds 
Av. 


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t Ov f^OO «f WO ^ 




00»-'-'WW'^'^t 
w to 00 O w to ao 
W tOX <- ro«« t^O 

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1 N n n 1 n 1 1 1 

i-i e» fo t«oo t^x O 






Kilo- 
grams to 
Pounds 
Av. 


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O PiXt« t'.'*50>0 
t af^oo f^ t^ WO « 
OO'-'^WWMfOt 

w tox o w tox 

<i to X *^ t^vit^O' 

M M M M M 




Hecto- 
grams (lOO 
grams) to 
Ounces Av. 


tx woo tX wo 
r* t w Oi t^ 5r •-• ^O 

W lOX O fOO Oi « t 

»';o«««o»-'Owt* 


£ 


•^ t^ o t r* •- tx ►- 

M M M f<« M n (^ 


O 


Kilo- 
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Grains. 


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^ 


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MUli- 
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to 
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OOOOOOMMti 




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1 1 n N n II n 1 n 

•-• w »*» t too r^x © 




Hekto- 
litres to 
Bushels. 


iOOtOOv)Ot/)OW) 
r^wiwc i^iowor^ 
f'jr^MioxwoO'^ 
XO»«f*3«- OX »^»o 




W lOX ^ t t>. Oi W IO 

M M )^ )^ n M 




Deka- 
litres to 
Gallons. 


r^ t w X to w o>0 f^J 
« '*j>nox o «-• »>o«« 
tx wo O viQit^t^ 
OwOi»«wxt»-ii^ 




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M M M M rii n 


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Litres to 
Quarts. 


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iom t^noo rt o^in »» 

©•"•■-WNf^iwjtw^ 


< 
a* 
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•^ w »>o t too r^x O 


Centilitres 
to Fluid 
Ounces. 


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f*5r^>-iioOkPiOOt 
f^O O r»50 O fO t^O 

OOl->MMWW(<«f«J 




Millilitres or 
Cu. Centi- 
litres to 
Fl. Drams. 


r^ t •-■ X «« w ©o <*i 
W lOX O f^OX « t 




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D n R D II n 

w n r^ t "/iO t*x O 



oi 



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•fl V 

w o^' 

<3B 

g a^ s - 8 2.2 

o** vag 
gE-3^2 ^2c° 



C! u c O d 



a 
c c go's 

- C.2 



.^ B c .2 



^•go 
J*:s « * s. " ♦* s 

3.flfe§9o"2.St3 
c** « C 5 « « t M c 

o a> ea ^ 2jBi3 2'3.« 
fl.tJ-^'SjQ ♦* « c 
S C ei 0-C.„ P»5 1 



s 

3 £• 

-•g 
V o 

go 

673 
•a 3 

I- 

"I 
••- a 

•fly 

>C3 



J 



Is 

o fl 

«j a 

d C 

•C •« 



11 



•g-g 








640 HEATING AND VENTILATING. 

Table No. II. 

EQUIVALENT VALUE OF UNITS IN BRITISH AND METRIC SYSTEMS. 

One foot = 12 inches = 30.48 centimetres =0.3048 metre. 

One metre = 100 centimetres = 3.2808 ft. = 1.094 yd. 

One mile = 5280 ft. = 1760 yd. = 1609.3 nietres. 

One foot = 144 sq. in, = i/9 sq. yd. = 929 sq. centimetres = 

.0929 sq. metre. 
One sq. metre = 10000 sq. centimetres = 1.1960 sq. yds.= 

10.764 sq. ft. 
One cubic foot = 1728 sq. in. = 2832 cu. centimetres = 0.02832 

cu. metres. 
One cubic metre = 35.314 cu. ft. = 1.3079 cu. yds. 
One pound adv. =7000 grains=i6 oz. =453.59 grains =0.45359 

kilograms. 
One kilogram = 1000 grams = 2.2046 lbs. = i5432 grains = 35.27 

oz. adv. 

COMPOUND UNITS. 

One foot-pound =0.13826 kg.-mt. = 1,3826 gr.-c. = 1/778 B.T.U. 
One horse-power = 33000 ft.-pound per minute = 746 Watts. 
One kilogram -metre = 7. 233 ft.-lb = 100,000 gr.-c. = 1/426 calorie. 
One gram-centimetre = i/iooooo kg.-mt. = .00007233 ft.-lb. 
One calorie = 426. 10 kg.-mt. = 3.9672 B.T.U. = 42000 million ergs 

per second =42 Watts. 
One B. T. U. = 778 ft.-lbs. =0.2521 cal. = 10820 mil. ergs. = 

107.37 kg.-m. 
One calorie per sq. metre = 0.3686 B.T.U. per sq. ft. 

C. G. S. SYSTEM. 

One d>Tie = one gram /981 =0.00215 lb. 

One erg. = 1 dyneXi cent. =0.0000707 ft.-lb. 

One Watt = 10 mil. ergs, per sec. =0738 ft.-lbs. per sec. = 

h. p. /746. 
One h. p. = 756 Watts. 



APPENDIX. 



541 



TABLE III.— REDUCTION TABLE. 

HEIGHT OF WATEK-COLUMN IN INCHES TO CORRESPOND TO VARIOUS PRESSURES 
IN OUNCES PER SQUARE INCH. TEliPERATURE SO** FAHR. 



Pressure 
in Os. 






per 






Sq. In. 


.0 


.1 







0.17 


I 


1.73 


1.90 


a 


3.46 


3-63 


3 


5. 19 


5-36 


4 


6.9a 


7-09 


5 


8.65 


8.8a 


6 


10.38 


10.55 


7 


13. II 


13. 38 


8 


13.84 


14.01 


9 


15-57 


15.74 



Decimal Parts of an Ounce. 



.3 



0.35 
3.08 
3.81 
5.54 
7.i7 
9.00 

10.73 
13.46 

14.19 
15-92 



.3 


.4 


.5 


0.52 


0.69 


0.87 


3.25 


a. 42 


2.60 


3-98 


4.15 


4-33 


5-71 


5.88 


6.06 


7.44 


7.61 


7.79 


9.17 


9.34 


9. 52 


10.90 


11.07 


11.36 


13.63 


13.80 


12.97 


14 36 
16. ov 


14-53 
16.36 


14.71 
16.45 



.6 



t: 



1.04 

2.77 
..so 

23 

7.96 

9.60 

11.43 

13.15 

88 

63 



II 



I. 31 
2.94 

I 8.13 
' 9.86 

11.60 
' 13.32 
,15.05 

16.79 



.8 



1.38 

3. II 

4.84 

6.57 

8.30 

10.03 

11.77 

13.49 

15.33 

16.96 



.9 



X.56 
3.29 
5. ox 

6.75 
8.48 
10. 31 
11.95 
13.67 
15.40 
17.14 



PRESSURES IN OUNCES PER SQUARE INCH CORRESPONDING TO VARIOUS HEADS OF 

W.\TER IN INCHES. 











Decimal Parts of an Inch. 








Head in 






















Inches. 
























.0 


.1 


.3 


.3 


.4 


.5 


.6 


.7 


.8 


.9 







0.06 


0.13 


0.17 


0.33 


0.39 


0.35 


0.40 


0.46 


0.53 


I 


0.58 


0.63 


0.69 


0.75 


0.81 


0.87 


0.93 


0.98 


X.04 


1.09 


3 


1. 16 


I. 31 


1.27 


1.33 


1.39 


1 44 


1.50 


1.56 


1.63 


1.67 


3 


1.73 


1.79 


1.85 


1.91 


1.96 


3.03 


3.08 


2.14 


3.19 


3.35 


4 


3.31 


2.37 


3.42 


3.48 


2.54 


3.60 


3.66 


3.72 


2.77 


3.83 


5 


3.89 


2.94 


3.00 


3.06 


3.12 


3.18 


3.24 


3.29 


3.35 


3.41 


6 


3.47 


3-52 


3.58 


3.64 


3.70 


3.75 


3.81 


3.87 


3.92 


3.98 


7 


4.04 


4. 10 


4. 16 


4.33 


4.28 


4 33 


4.39 


4.45 


4.50 


4.56 


8 


4.62 


4.67 


4-73 


4. 70 


4.85 


4.91 


4-97 


5 03 


5.08 


5.14 


9 


5.30 


5.26 


5.31 


5.37 


5.42 


5 48 


5.54 


5.60 


5.66 


5.72 



T.\BLE IV.— TABLE OF PROPERTIES OF GASES. 



Element or Compound. 



Oxygen 

Nitrogen 

Hydrogen 

Argon 

Carbon 

Phosphorus 

Sulphur 

Silicon 

Air 

Water- vapor 

Ammonia 

Carbon monoxide 

(Carbonic oxide) 
Carbon dioxide 

(Carbonic acid) 

Olefiant gas 

Marsh gas 

Sulphurous acid 

Sulphuretted hydrogen 
Bisulphuret of carbon . 

Orone 



Symbol by 
Volume. 



O 

N 
H 

C 
P 
S 
Si 
79N -h3iO 
HiO 
NHa 
CO 

COi 

CHi 

CH« 

SO» 

SHj 

SjC 

Oi 



Atomic 
Weights. 



16 

14 
I 

19 

13 

31 
32 

14 



:8 

17 
38 

44 

14 
16 

64 

34 
76 

24 



Cubic 

Feet 

per Lb. 

at 62'. 



11.88 

13.54 
i«9.7 

15^84 ' 
6. 119 
5.932 

13-55 

13.14* 
31 .07 

33.3 
13.6 

8.64 

13.587 

23-757 

6.463 

5.582 

2.487 

7-97 



Weight 
per Cu. 
Ft. at 
63°. Lbs. 



0.0814 
0.0738 
0.00527 



63131 
16337 
1 686 1 
07378 
0761 

0.04745 

0.0448 

0.07364 

o. I 163 I 



o 
o 
o 
o 
o 

o 



0736 

,04200 

15536 

17018 

.40052 

, 1 2648 



Specific 

Gravity 

at 63°. 

Water -I. 



Relative 
Density. 



o 

o 

o 

o 

o 

o 

o 

o 

o. 

0.0007613I0 

0.00118 

0.003369 



001350 

001185 

0000846 o 

001607 

,001013 

.0036331 

. 003705 

.001T84 

.001221 



I 
o 

2 

3 

I 

II 



0.00187 

0.001181 
0.000675 

0.0O34Q3 
0.002877 
0.00643 

0.00203 



10563 

97137 
,06936 
,3118 

83333 
.1877 
.3150 
.01033 
.0000 

6353 
.5893 

9674 



I . 52901 



967104 
55306 
54143 
3943 
5 . 3007 

I . 64656 



♦ By this table there wo:ild be 12.75 cubic feet of air at 32® per pound. 



542 



HEATING AND VENTILATING. 



TABLE v.— TABLE OF CIRCLES, SQUARES. AND CUBES. 



fl 


nw 


n* — 

4 


n* 


«« 


vT 


<^ 


Diam. 


Circumf. 


Area. 


Square. 


Cube. 


Sq. Root. 


Cub. Rt. 


I.O 


3 142 


0.7854 


1. 000 


1. 000 


I. 0000 


1 I. 0000 


I.I 


3 456 


0.9503 


1. 210 


^331 


1.0488 


1 0323 


1.2 


3 770 


1.13x0 


1.440 


1.728 


I 0955 


1.0627 


1.3 


4.084 


1.3273 


1.690 


2.197 


I. 1402 


I. 0914 


1.4 


4.398 


1.5394 


1.960 


2.744 


I. 1832 


1.I187 


1-5 


4.712 


1.7672 


2.250 


3-375 


I . 2247 


1.1447 


1.6 


5 027 


2.0106 


2.560 


4.096 


1.2649 


I. 1696 


1.7 


5341 


2.2698 


2.890 


4 913 


1-3038 


1 1935 


1.8 


5-655 


2.5447 


3.240 


5-832 


I. 3416 


I. 2164 


1-9 


5 969 


2.8353 


3.610 


6.859 


1-3784 


1.2386 


2.0 


6.283 


3.1416 


4.000 


8.000 


I. 4142 


1.2599 


2.1 


6.597 


3 4636 


4.410 


9.261 


1.4491 


1.2806 


2.2 


6.912 


3.8013 


4-840 


10.648 


1.4832 


1.3006 


2.3 


7.226 


4.1548 


5.290 


12.167 


1.5166 


1.3200 


24 


7.540 


4 5239 


5760 


13.824 


1.5492 


I 3389 


25 


7.854 


4.9087 


6.250 


15.625 


1.5811 


1 3572 


2.6 


8.168 


5.3093 


6.760 


17 576 


1.6125 


I 3751 


2.7 


8.482 


5.7256 


7.290 


19 683 


1.6432 


1 3925 


2.8 


8.797 


6.1575 


7-840 


21.952 


1.6733 


1.4095 


2.9 


9. Ill 


6.6052 


8.410 


24 389 


I . 7029 


1.4260 


30 


9.425 


7.0686 


9.00 


27.000 


I. 7321 


1.4422 


31 


9.739 


7-5477 


9.61 


29.791 


1.7607 


1.4581 


32 


XO.053 


8.0425 


10.24 


32.768 


1.7889 


1.4736 


3 3 


10.367 


8.5530 


10.89 


35.937 


I. 8166 


1.4888 


3 4 


10.681 


9.0792 


11.56 


39-304 


1.8439 


I - 5037 


3 5 


XO.996 


9.6211 


12.25 


42.875 


1.8708 


1.5183 


3.6 


II. 310 


10.179 


12.96 


46.656 


1.8974 


I 5326 


3-7 


11.624 


10.752 


13.69 


50.653 


I 9235 


I 5467 


3-8 


11.938 


11.341 


14.44 


54 872 


1.9494 


1.5605 


3.9 


12.252 


I I . 946 


15.21 


59-319 


1-9748 j 


1 5741 


4.0 


12.566 


12.566 


16.00 


64.000 


2.0000 1 


I 5874 


4.1 


12.881 


13 203 


16.81 


68.921 


2.0249 


1.6005 


4.2 


13 195 


13-854 


17.64 


74.088 


2.0494 


1.6134 


4.3 


13 509 


14-522 


18.49 


79 507 


2.0736 


I. 6261 


4.4 


^S-^2S 


15-205 


19.36 


85.184 


2.0976 


1.6386 


4.5 


14137 


15-904 


20.25 


91.125 


2.1213 


1.6^10 


4.6 


14 451 


16.619 


21.16 


97-336 


2.1448 


1.6631 


4-7 


14.765 


17-349 


22.09 


103.823 


2.1680 


1.6751 


4.8 


15.080 


18.0Q6 


23 04 


110.592 


2.1909 


1.6869 


4.9 


15-394 


18.857 1 

i 


24.01 


117.649 


2.2136 1 


1.6985 



APPENDIX. 



543 



TABLE \ .-Continued, 



n 


HW 


4 


H* 


«> 


vT 


<^ 


Diam. 


Circiunf, 


Area. 


Square. 


Cube. 


Sq. Root. 


Cub. Rt. 


50 


15.708 


19 635 


25.00 


125.000 


2.2361 


I. 7100 


5.1 


16.022 


20.428 


26.01 


132.651 


2.2583 


I. 7213 


. 52 


16.336 


21.237 


27.04 


140.608 


2.2804 


1.7325 


5.3 


16.650 


22.062 


28.09 


148.877 


2.3022 


I . 7435 


5-4 


16.965 


22.902 


29.16 


157.464 


2.3238 


1.7544 


5-5 


17.279 


23 . 758 


30.25 


166.375 


2.3452 


I . 7652 


5.6 


17.593 


24.630 


31 36 


175.616 


2.3664 


1.7758 


5-7 


17.907 


25.518 


32.49 


185 . 193 


2.3875 


I 7863 


5.8 


18.221 


26.421 


33.64 


195. "2 


2.4083 


1.7967 


5 9 


18.535 


27.340 


34.81 


205.379 


2.4290 


1.8070 


6.0 


18.850 


28.274 


36.00 


216.000 


2.4495 


1.8171 


6.1 


19.164 


29.225 


37.21 


226.981 


2.4698 


1.8272 


6.2 


19.478 


30.191 


38.44 


238.328 


2.4900 


I. 8371 


6.3 


19.792 


31.173 


39 69 


250.047 


2.5100 


1.8469 


6.4 


20.106 


32.170 


40.96 


262.144 


2.5298 


1.8566 


6.5 


20 . 420 


33.183 


42.25 


274.625 


2.5495 


1.8663 


6.6 


20.735 


34-212 


43 56 


287.496 


2.5691 


1.8758 


6.7 


21.049 


35 257 


44.89 


300.763 


2.5884 


1.8852 


6.8 


21.363 


36.317 


46.24 


314.432 


2.6077 


1.8945 


6.9 


21.677 


37.393 


47.61 


328.509 


2.6268 


X.9038 


7.0 


21.991 


38.485 


49 00 


343 000 


2.6458 


I. 9129 


7.1 


22.305 


39.592 


50.41 


357. 9" 


2.6646 


1.9220 


7.2 


22.619 


40.715 


51.84 


373 248 


2.6833 


I. 9310 


7.3 


22.934 


41.854 


53.29 . 


389.017 


2 . 7019 


I 9399 


7.4 


23 . 248 


43.008 


54.76 


405.224 


2.7203 


1.9487 


75 


23 . 562 


44 179 


56.25 


421.875 


2.7386 


1.9574 


7.6 


23.876 


45 365 


57.76 


438.976 


2.7568 


I. 9661 


7.7 


24.190 


46.566 


59.29 


456.533 


2.7749 


I 9747 


7.8 


24.504 


47 . 784 


60.84 


474.552 


2 . 7929 


1.9832 


7 9 


24.819 


49.0x7 


62.41 


493 039 


2.8107 


Z.9916 


8.0 


25.133 


50 . 266 


64.00 


512.000 


2.8284 


2.0000 


8.1 


25.447 


51.530 


65.61 


531.441 


2.8461 


2.0083 


8.2 


25.761 


52.810 


67.24 


551.468 


2.8636 


2.0165 


8.3 


26.075 


54 106 


68.89 


571.787 


2.8810 


2 . 0247 


8.4 


26.389 


55.418 


70.56 


592 . 794 


2.8983 


3.0328 


8.5 


26 . 704 


56 . 745 


72.25 


614.125 


2 9155 


2.0408 


8.6 


27.018 


58.088 


73 96 


636.056 


2.9326 


2.0488 


8.7 


27.332 


59.447 


75.69 


658 . 503 


2.9496 


2.0567 


8.8 


27.646 


60.821 


77.44 


681.473 


2.9665 


2.0646 


8.9 


27.960 


62.211 


79.21 


704.969 


2.9833 


2.0724 


9.0 


28.274 


63.617 


81.00 


729.000 


3.0000 


2.0801 


9.1 


28.588 


65.039 


82.81 


753.571 


3.0166 


2.0878 


9.2 


28.903 


66.476 


84.64 


778.688 


3.0332 


2.0954 


9-3 


29.217 


67.929 


86.49 


804.357 


3.0496 


2 . 1029 


9-4 


29 531 


69.398 


88.36 


830.584 


3 0659 


2.1105 



544 



HEATING AND VENTILATING. 



TABLE \ ,—Cofainued. 



n 


nw 


4 


M> 


«> 


V^ 


^ 


Diam. 


Circumf. 


Area. 


Square. 


Cabe. 


Sq. Root. 


Cub. Rt. 


9 5 


29 845 


70.882 


90.25 


857.37s 


3.0822 


2.1179 


9.6 


30 159 


72.382 


92.16 


884.736 


3 0984 


2.1253 


9 7 


30 -473 


73 898 


94 09 


912.673 


3 "45 


2.1327 


9.8 


30.788 


75 430 


96.04 


941.192 


3 1305 


2.1400 


9 9 


31 102 


76.977 

• 


98.01 


970.299 


3 1464 


2.1472 


10. 


31.416 


78 S40 


100.00 


1000.000 


3 1623 


2 1544 


10. 1 


31 730 


80.119 


102.01 


1030.301 


3 1780 


2.1616 


10.2 


32 044 


81.713 


104.04 


1061 . 208 


3 1937 


2.1687 


10 3 


32.358 


83.323 


106.09 


1092.727 


3 2094 


2 1757 


10.4 


32.673 


84.949 


108.16 


1124.863 


3 2249 


2.182S 


10.5 


32.987 


86.590 


110.25 


1157 625 


3 2404 


2.1897 


10.6 


33 301 


88.247 


112.36 


I 191. 016 


3 2558 


2.1967 


10.7 


33 615 


89.920 


114.49 


1225.043 


3.2711 


2.2036 


10.8 


33 929 


91.609 


116.64 


1259.712 


3.2863 


2.2104 


10.9 


34.243 


93 313 


118. 81 


1295.029 


3 3015 


2.2172 


II. 


34 . 558 


95 033 


121.00 


1331.000 


3.3166 


2.2239 


II. I 


34 872 


96.769 


123.21 


1367.631 


3 3317 


2.2307 


II. 2 


35 186 


98.520 


125.44 


1404.928 


3-3466 


2.2374 


"3 


35 500 


100.29 


127.69 


1442.897 


3.3615 


2.2441 


II. 4 


35 814 


102.07 


1 29 . 96 


1481.544 


3.3764 


2.2506 


II 5 


36.128 


103 87 


132.25 


1520.87s 


3.3912 


2.2572 


11.6 


36.442 


105 . 68 


134 56 


1560.896 


3.4059 


2.2637 


II. 7 


36.75" 


107.51 


136.89 


1601.613 


3 4205 


2.2702 


II. 8 


37071 


109.36 


130 2 1 


1643.032 


3.4351 


2.2766 


II. Q 


37.385 


III. 22 


141. 61 


1685.159 


34496 


2.2SSI 


12.0 


37 60Q 


113 10 


144 00 


1728.000 


3.4641 


2.2894 


12. 1 


38.013 ! 


114.99 


146.41 


1771 561 


3 4785 


2.2957 


12. 2 


38.327 


116. QO 


148.84 


1815.848 


3 4928 


2.3021 


I-' 3 


38.642 ' 


118.82 


151 2Q 


1860.867 


3 5071 


2.3084 


12.4 


38.956 , 

1 


120.76 


153 76 


1906.624 


3.5214 


2.3146 


1-^5 


30 270 


1 
122.72 


156.25 


1953 125 ! 


3 5355 


2.3208 


12.0 


30 584 


124 6q I 


158.70 


2000.376 


3 5496 


2.3270 


12.7 


30 SgS 


1JO.68 


lOl . 20 


2048.383 ' 


3 5637 


2 35.i^ 


12 8 


40 2 1 2 


128.08 


163.84 


2007 152 ' 


3 5777 


2 3392 


12 g 


40.527 1 


130.70 


l()0.4i 


2146.680 

1 


3 5917 


2 3453 


1.; 


40.S41 i 


132 73 


iChj.oo 


1 

2107 000 


3 6056 


2 3513 


»3 I 


41 155 


134 78 


171 .(?i 


2248 001 


3 6194 


2 3573 


1.^ ^ 


41 4f'0 


i^;o 85 


174 24 


2:00 908 


3 6332 


2 3<y5S 


13 J 


41 783 


138 Q3 


1 70 . So 


235-' 037 


3.6469 


2 3^3 


13 4 


42 cx)7 

1 


141 03 


1 70 5<^ 


J406 . 104 


3.6606 


2 3752 


13 5 


4- 41: 


U.^ 14 


iS: :;; . 

1 


-4^ 375 i 


3 6742 


2.3811 


13 t> 


4- 7-<» 


U5 -7 


I.S4 0'> ' 


-515 456 I 


3 6878 


2 3870 


»3 7 


43 040 


147 41 


1S7 C»o , 

I 


-571.353 1 


3 7013 


2.SQ'^ 


13 s 


4^ .N>4 


UO 5' 


100 44 1 


202^.O72 


3 7148 


2.3086 


i.^ 


4.; IM»S 


151 75 


10.^ :i 1 


2085 Mo 


i -^-^s 


2 4044 



APPENDIX. 



646 



TABLE y.-<:ofUinued. 



n 


nr 


4 


n* 


«> 


V5r 


<^ 


Diazn. 


Circumf. 


Area. 


Square. 


Cube. 


Sq. Root. 


Cub. Rt. 


14.0 


43 932 


153 94 


196.00 


2744.000 


3 7417 


2.4x01 


14. 1 


44.296 


156.15 


198.81 


2803.221 


3.7550 


2.4159 


14.2 


44.611 


158.37 


201 . 64 


2863 . 288 


3.7683 


2.4216 


14.3 


44 925 


160.61 


204.49 


2924 . 207 


3.7815 


2.4272 


14.4 


45 . 239 


162.86 


207.36 


2985.984 


3.7947 


2.4329 


14 5 


45-553 


165.13 


210.25 


3048.625 


3.8079 


2.438s 


14.6 


45.867 


167.42 


213.16 


3112.136 


3 8210 


2.4441 


14.7 


46.181 


169.72 


216.09 


3176.523 


3.8341 


2.4497 


14.8 


46.496 


172.03 


219.04 


3241.792 


3.8471 


2.4552 


14.9 


46.810 


174.37 


222.01 


3307.949 


3.8600 


2.4607 


15.0 


47 124 


176.72 


225.00 


3375.000 


3.8730 


2.4662 


15.1 


47.438 


179.08 


228.01 


3442.951 


3.8859 


2.4717 


IS 2 


47.752 


181.46 


231.04 


3511.808 


3.8987 


2.4772 


15 5 


48.066 


183.85 


234.09 


3581.577 


3.9"5 


2.4825 


154 


48.381 


186.27 


237.16 


3652.264 


3.9243 


2.4879 


155 


48.695 


188.69 


240.25 


3723.875 


3 9370 


2.4933 


15.6 


49.009 


191. 13 


243 36 


3796.416 


3.9497 


2.4986 


15.7 


49 323 


193 . 59 


246.49 


3869.893 


3-9623 


2 . 5039 


15.8 


49.637 


196.07 


249.64 


3944.312 


3-9749 


2.5092 


15 9 


49.951 


198.56 


252.81 


4019.679 


3.987s 


2.5146 


16.0 


50.265 


201.06 


256.00 


4096.000 


4.0000 


2.5198 


16. 1 


50.580 


.203 . 58 


259.21 


4173.281 


4.0125 


2.5251 


16.2 


50 894 


206.12 


262.44 


4251.528 


4.0249 


2 5303 


16.3 


51.208 


208.67 


265.69 


4330.747 


4 0373 


2. 5355 


16.4 


51-522 


•211 .24 


268.96 


4410.944 


4.0407 

• 


2.5406 


16.5 


• 51-836 


213.83 


272.25 


4492.125 


4.0620 


2 . 5458 


16.6 


52.150 


216.42 


275.56 


4574.296 


4 0743 


2.5509 


16.7 


5-' 465 


219.04 


278.89 


4657.463 


4.0866 


2.5561 


16.8 


1 52.779 


221.67 


282 . 24 


4741.632 


4.0988 


2.5612 


16.9 


53.093 


224.32 


285.61 


4826.809 


4. mo 


2 . 5663 


17.0 


1 53 407 


226.98 


289.00 


4913.000 


4.1231 


2.5713 


17. 1 


1 53 721 


229.66 


292.41 


5000.211 


4.1352 


2 5763 


17.2 


54 035 


132.35 


295.84 


5088.448 


4.1473 


2.5813 


17.3 


54-350 


23506 


299.29 


5177.717 


4.1593 


2.5863 


174 


54.664 


237-79 


302.76 


5268.024 


4.1713 


2.5913 


17.5 


54.978 


240.53 


306.25 


5359-375 


4.1833' 


2.5963 


17.6 


55 292 


2*3 29 


309 76 


5451 776 


4.1952 


2.6012 


17.7 


55 606 


246.06 


313 2Q 


5545 233 


4.2071 


2.6061 


17.8 


55 920 


248 . 85 


316.84 


5639-752 


4.2190 


2.6109 


17.9 


56.235 


251-65 


320.41 


5735-339 


4.2308 


2.6158 


18.0 


56 549 


25447 


324.00 


5832.000 


4.2426 


2.6207 


18. 1 


56.863 


257 30 


327.61 


592Q.741 


4.2544 


2.6256 


18.2 


57-177 


260. 16 


331.24 


6028. 56S 


4.2661 


2.6304 


18.3 


57-491 


263 . 02 


334.89 


6128.487 


4.2778 


2.6352 


18.4 


57-805 


205.90 


338.56 


6220.504 


4.2895 


2 . 6401 



546 



HEATING AND VENTILATING. 



TABLE \,— Continued, 



n 


nw 


A 


n* 


fi« 


vir 


<^ 


Diam. 


Circumf. 


Area. 


Square. 


Cube. 


Sq. Root. 


Cub. Rt. 


i8.S 


58.119 


268.80 


342.25 


6331.625 


4.3012 


2.6448 


18.6 


58.434 


271.72 


345 96 


6434.856 


4.3x28 


2.649s 


18.7 


58.748 


274.65 


349.69 


6539.203 


4 3243 


2.6543 


18.8 


59 062 


277.59 


353 44 


6644.672 


4 3359 


2-6590 


18.9 


59.376 


280.55 


357.21 


6751.269 


4.3474 


2.6637 


19.0 


59.690 


283 . 53 


361.00 


6859.000 


4.3589 


2.6684 


10. 1 


6o.cx>4 


286.52 


364.81 


6967.871 


4.3703 


2.6731 


19.2 


60.319 


289.53 


368.64 


7077.888 


4.3818 


2.6777 


193 


60.633 


292.55 


372.49 


7189.057 


4 3932 


2.6824 


19.4 


60.947 


295 . 59 


376.36 


7301.384 


4 4045 


2.6869 


19 5 


61 . 261 


298.65 


380.25 


7414.875 


4.4159 


2.6916 


19.6 


61.575 


301.72 


384.16 


7529.536 


4.4272 


2.6962 


19.7 


61.889 


304.81 


388.09 


7645.373 


4 4385 


2.7008 


19.8 


62 . 204 


307.91 


392.04 


7762.392 


4 4497 


2 ■ 7053 


19.9 


62.518 


311 03 


396.01 


7880.599 


4.4609 


2.7098 


20.0 


62.832 


314.16 


400.00 


8000.000 


4.4721 


2.7144 


20.1 


63 . 146 


317.31 


404.01 


8120.601 


4 4833 


2.7189 


20.2 


63.460 


320.47 


408.04 


8242.408 


4.4944 


2.7234 


20.3 


63.774 


323.66 


412.09 


8365.427 


4 505s 


2.7279 


20.4 


64.088 


326.85 


416.16 


8489.664 


4.5166 


2.7324 


20.5 


64.403 


330.06 


420.25 


8615.125 


4.5277 


2.7368 


20.6 


64.717 


333 29 


424.36 


8741.816 


4.5387 


2.7413 


20.7 


65.031 


336 . 54 


428.49 


8869 . 743 


4 5497 


2 . 7457 


20.8 


65 345 


339 80 


432.64 


8989.912 


4 5607 


2 . 7502 


20.9 


65 659 


343 07 

• 


436.81 


9129.329 


4.5716 


2. 7545 


21 .0 


65 -973 


346.36 


441.00 


9261.000 


4.5826 


2.7589 


21. 1 


66 . 288 


349 67 


445.21 


9393 931 


4 .«>935 


2 7633 


21.2 


66.602 


352.99 


449 44 


9528.128 


4.6043 


2 . 7676 


21.3 


66.916 


356.33 


453 69 


9663.597 


4.6152 


2.7720 


21.4 


67 . 230 


359 68 


457 96 


9800.344 


4.6260 


2.7763 


21.5 


67 . 544 


363 05 


462.25 


9938.375 


4 6368 


2.7806 


21.6 


67.858 


366.44 


466.56 


10077.696 


4.6476 


2.7849 


21.7 


68.173 


369.84 


470.89 


10218.313 


4 6583 


2.7893 


21.8 


68.487 


373 25 


475-24 


10360.232 


4.6690 


2 . 7935 


21 .9 


68.801 


376.69 


479 61 


10503.459 


4 6797 


2 . 7978 


22.0 


69.115 


380.13 


484.00 


10648.000 


4.6904 


2.8021 


22.1 


69.429 


383 60 


488.41 


10793.861 


4.7011 


2.8063 


22.2 


69 743 


387 08 


492.84 


10941.048 


4.7117 


2.8105 


22.3 


70.058 


390.57 


497 .29 


11089.567 


4.7223 


2.8147 


22.4 


70.372 


394.08 


SOI . 76 


11239.424 


4.7329 


2.8189 


22.5 


70.686 


397.61 


506.25 


11390.625 


4.7434 


2.8231 


22.6 


71.000 


401.15 


510.76 


11543.176 


4 . 7539 


2.8273 


22.7 


71 314 


404.71 


515 29 


11697.083 


4.7644 


2.8314 


22.8 


71.268 


408.28 


519 84 


11852.352 


4.7749 


2.8356 


22.9 


71.942 


411.87 


524 41 


1 2008 . 989 


4.7854 


2 8397 



APPENDIX. 
TABLE \.—Conluiued. 



n 


« 


»t^ 


■f 


■■ 


vT 


<^ 


Dkm. 


Circomf. 


A««. 


Sq«.«. 


Cub«. 


So. Root. 


Cub. Rt. 


»3-0 


7' .157 


41S-48 


529 00 


12167.000 


4 79S8 


3.8438 


13- 1 


72.571 


419 10 


533-61 


12336.391 


4.8062 


3-8479 


»3-3 


73-885 


422.73 


538-24 


13487.168 


4,Si66 


2-8521 


»3.3 


73 199 


436.39 


543-89 


13649 337 


4.8370 


2.8561 


»3* 


73SI3 


430.0s 


547-56 


13813.904 


4 8373 


3,8603 


»3.S 


73-827 


433-74 


552.25 


13977.875 


4-8477 


2.8643 


136 


74 '43 


437-44 


556-96 


13144 356 


4.8580 


3,8684 


»3-7 


74 456 




561.69 


1331 '.053 


4-8683 


3.8724 


=38 


74.770 


444-88 


566.44 


13481-273 


4.878s 


2,876s 


33 9 


75084 


448.63 


571-21 


13651-919 


4. 8888 


2.8«os 


34 


75-398 


453-39 


576,00 


13834.000 


4-8990 


2.8845 


H.i 


7S-7II 


456-17 


580.81 


13997.531 


4,9093 


2.888s 




76.037 


459-96 


585-64 


14172.488 


4.9193 


2.892s 


14-3 


76 - 341 


463-77 


S90.49 


14348.907 


4-9295 


3.896s 


»*■* 


76.655 


467-60 


595 36 


14536.784 


4-9396 


2.9004 


145 


76.969 


471 44 


600.25 


14706.125 


4-9497 


3-9044 


»4 6 


77-283 


475-39 


605.16 


14886.936 


4.9598 


2.9083 




77-597 


479 16 




15069.223 


4 9699 


2 9133 


»4-8 


77.911 


483-05 


615.04 


15252.993 


4,9799 


2.9162 


149 


78.226 


486.96 


620-01 


15438.249 


49899 


2.9201 


3S0 


78.540 


490-87 


635.00 


15625 000 


S-0000 


2.9241 


>S I 


78.854 


494. Si 


630.01 


15813-251 


5 0099 


3 9279 


25-1 


79-168 


498-76 


63s 04 


16003. ooS 


S-0199 


39318 


35-3 


79 482 


502.73 


640,09 


16194.377 


5,0199 


2-9356 


JS.4 


79 796 


506.71 


645 16 


16387.064 


5 -0398 


3 9395 


JSS 


8o.t:i 


S10.71 


650.35 


16581.375 


50497 


3-9434 


»S6 


80.425 


5M 73 


655-36 


16777,316 


5-0596 


3 9473 


iS-7 


80.739 


518-75 


660.49 


16974.593 


5,0695 


2.9510 


JS.8 


81 .053 


533.79 


665,64 


17173-512 


5-0793 


3 -9549 


»S0 


81.367 


526.85 


670.81 


17373,979 


S-0893 


3.9586 


16.0 


81.681 


530.93 


676-00 


17576-000 


5 0990 


2.9624 


a6.i 


81.996 


535 02 


681.21 


17779.581 


5-108S 


2.9662 


16.2 


82.310 


539 13 


686-44 


17984-738 


5 118s 


2.9701 


»6.3 


83.624 


543 25 


691.69 


18191.447 


5-1383 


3-9738 


.6.4 


83.938 


547-39 


696.96 


18399.744 


5-138^ 


2.9776 


»6.s 


83.252 


SSI S5 


702.25 


18609.635 


5-1478 


3-9S14 


16.6 


83.566 


SSS-72 


707.56 


18821.096 


S-IS7S 


3-9851 


26 7 


83881 


559-90 


712,89 


19034 163 


5,1673 


2.9888 


26 S 


84-195 


564.10 


718.34 


19348,833 


5- 1768 


3.W^6 


26.9 


84.509 


S68.33 


733-61 


19465-109 


5-1865 


J 9963 


2;,o 


84-823 


573-56 


729-00 


19683,000 


S..963 


3-0000 


27 I 


85-137 


576.80 


734-41 


19902.511 


S-30S7 


3 0037 


27.2 


85-451 


581.07 


73984 


20.23.648 


5 3153 




27.3 


85-765 


S8S-3S 


745-29 


30346,417 


5.3349 


3-0111 


'7-4. 


86. 080 


589.65 


750-76 


20570.834 


S-334S 


3-0147 



548 



HEATING AND VENTILATING. 



TABLE W.— Continued. 



n 


nw 


1^ 

4 


M> 


fi> 


■y/S" 


^ 


Diaxn. 


Circumf. 


Area. 


Square. 


Cube. 


Sq. Root. 


Cub. Rt. 


27. 5 


86.394 


593 96 


756.25 


20796 . 875 


52440 


3 0184 


27.6 


86.708 


598 29 


761 . 76 


21024.576 


5 .2535 


3.0221 


27.7 


87.022 


602.63 


767 . 29 


21253-933 


5 . 2630 


3 0257 


27.8 


87.336 


606.99 


772.84 


21484.952 


5.2725 


3 0293 


27.9 


87.650 


611.36 


778.41 


21717.639 


5 . 2820 


3 0330 


28.0 


87-965 


615.75 


784.00 


21952.000 


5. 2915 


3.0366 


28.1 


88.279 


620.16 


789.61 


22188.041 


5.3009 


3 0402 


28.2 


88 593 


624.58 


795 24 


22425.768 


5 3103 


3 0438 


28.3 


88.907 


629.02 


800.89 


22665.187 


5 3197 


3 0474 


28.4 


89.221 


633.47 


806.56 


22906.304 


5.3291 


3.0510 


28.5 


89.53s 


637 94 


812.25 


23149.125 


5 3385 


3 0546 


28.6 


89.850 


642.42 


817.96 


23393 656 


5.3478 


3.0581 


28.7 


90.164 


646.93 


823.69 


23639 903 


5 3572 


3.0617 


28.8 


90.478 


651.44 


829.44 


23887.872 


5 3665 


3 0652 


28.9 


90.792 


655.97 


835.21 


24137.569 


5.3758 


3 0688 


29.0 


91.106 


660.52 


841.00 


24389.000 


5.3852 


3-0723 


29.1 


91.420 


665.08 


846.81 


24642.171 


5 3944 


3.0758 


29.2 


91-735 


669.66 


852.64 


24897.088 


5 4037 


3 0794 


29 3 


92.049 


674 . 26 


858.49 


25153.757 


5-4129 


3 0829 


29.4 


92.363 


678.87 


864.36 


25412.184 


5.4221 


3 0864 


29 5 


92.677 


683.49 


870.25 


25672.375 


5 4313 


3 0899 


29.6 


92.991 


688.13 


876.16 


25934 336 


5.4405 


3 0934 


29 7 


93-305 


692.79 


882.09 


26198.073 


'5 4497 


3.0968 


29.8 


Q3.619 


697.47 


888.04 


26463 . 592 


5.4589 


3 1003 


29.9 


93 934 


702.15 


894.01 


26730.899 


5.4680 


3 1038 


30.0 


94-248 


706.86 


900.00 


27000.000 


5.4772 


3.1072 


30.1 


94.562 


711.58 


906.01 


27270.901 


5 4863 


3.1107 


30.2 


94-876 


716.32 


912.04 


27543.608 


5.4954 


3. "41 


303 


95.190 


721 .07 


918.09 


27818.127 


5.5045 


3 1176 


304 


95 . 50s 


725.83 


924.16 


28094.464 


5 S136 


3 1210 


30. s 


95.819 


730.62 


930.25 


28372.625 


5.5226 


3 1244 


30.6 


96.133 


735.42 


936.36 


28652.616 


5.5317 


3.1278 


30 7 


96.447 


740.23 


942.49 


28934.443 


5 5407 


3.1:^12 


30.8 


96.761 


745.06 


948 . 64 


29218. 112 


5 . 5497 


3 1346 


30.9 


97.075 


749.91 


954 - 81 


29503.629 


5 5587 


3 1380 


31.0 


97 389 


754.77 


961.00 


29791.000 


5 5678 


3.1414 


31 I 


97 • 704 


759 65 


967.21 


30080.231 


5 5767 


3 1448 


31.2 


98.018 


764.54 


973 44 


30371.328 


5.5857 


3.1481 


31 2 


98.332 


769.45 


979.69 


30664 . 297 


5 5946 


3151S 


31 4 


98.646 


774.37 


985.96 


30959 144 


5 6035 


3.1548 


31 5 


98.960 


779.31 


992.25 


31255 875 


5.6124 


3.1582 


31 6 


99.274 


784.27 


998.56 


31554 496 


5 6213 


3 1615 


31 7 


99 588 


789.24 


1004.89 


31855.013 


5 6302 


3.1648 


31-8 


99.903 


794-23 


loii .24 


32157.432 


5 6391 


3.1681 


31 9 


100.22 


799 23 


1017.61 


32461.759 


5 6480 


3-1715 



APPENDIX. 



549 



TABLE \,— Continued. 



n 


nw 


•^T 


M> 


«> 


vr 


<r^ 


Diam. 


Circumf. 


Area. 


Square. 


Cube. 


Sq. Root. 


Cab. Rt. 


32.0 


100.53 


804.25 


1024.00 


32768.000 


5.6569 


3.1748 


321 


100.85 


809.28 


1030.41 


33076.161 


5.6656 


3.1781 


32.2 


lOI . 16 


814.33 


1036.84 


33386.248 


5.6745 


3.1814 


32.3 


101.47 


819.40 


1043.29 


33698.267 


5.6833 


3.1847 


324 


loi . 79 


824.48 


1049.76 


34012.224 


5.6921 


3.1880 


32.5 


102.10 


829 . 58 


1056.25 


34328.125 


S.7008 


3.1913 


32.6 


102.42 


834.69 


1062.76 


34645 976 


5.7096 


3.1945 


32.7 


102 . 73 


839 82 


1069.29 


34965 - 783 


5.7183 


3.1978 


32.8 


X03.04 


844.96 


1075.84 


35287.552 


5.7271 


3 . 2010 


32.9 


103.36 


850.12 


1082.41 


35611.289 


5 . 7358 


3.2043 


33 


103.67 


855.30 


1089.00 


35937.000 


5.7446 


3.207s 


33.1 


103.99 


860.49 


1095.61 


36264.691 


5.7532 


3.2108 


33-2 


104.30 


865.70 


1102.24 


36594.368 


5.7619 


3.2140 


33-3 


104.62 


870.92 


1108.89 


36926.037 


5.7706 


3 2172 


33-4 


104.93 


876.16 


i"5 56 


37259.704 


5.7792 


3.2204 


33. 5 


105.24 


881.41 


1122.25 


37595-375 


5 • 7879 


3 2237 


33-6 


105.56 


886.68 


1128.96 


37933 056 


5-7965 


3 2269 


33.7 


105.87 


891.97 


"35-69 


38272.753 


5.8051 


3 2301 


33.8 


106.19 


897.27 


1142.44 


38614.472 


5-8137 


3-2332 


330 


106.50 


902.59 


I 149 21 


38958.219 


S.8223 


3 . 2364 


34 


106.81 


907.92 


1156.00 


39304.000 


5-8310 


3.2396 


34 X 


107.13 


913.27 


1162.81 


39651.821 


5-8395 


3.2428 


34 2 


107.44 


918.63 


1169.64 


40001.688 


5 8480 


3 2460 


34.3 


107 . 76 


924 01 


1176.49 


40353.607 


5 8566 


3 2491 


34 4 


108.07 


929.41 


1183.36 


40707 . 584 


5.8651 


3.2522 


34. 5 


108.38 


934 82 


1190.25 


41063.625 


5.8736 


3.2554 


34.6 


108.70 


940.25 


1197.16 


41421.736 


5.8821 


3 . 2586 


34 7 


109.01 


945 69 


1 204 . 09 


41781.923 


5-8906 


3-2617 


34.8 


109.33 


951.15 


1 21 1 .04 


42144.192 


5 89QI 


3 2648 


34.9 


109.64 


956.62 


1218.01 


42508.549 


5 9076 


3 . 2679 


350 


109.96 


962.11 


1225.00 


42875.000 


5.9161 


3 2710 


351 


110.27 


967.62 


1232.01 


43243 551 


5 9245 


3.2742 


35 2 


110.58 


973-14 


1239.04 


43614.208 


5 9329 


3 2773 


35 3 


110.90 


978.68 


1 246 . OQ 


43986.977 


5 9413 


3 2804 


35-4 


III. 21 


984 23 


1253.16 


44361.864 


5 9497 


3 - 283s 


355 


I" 53 


989.80 


1260.25 


44738.875 


5 9581 


3.2866 


35-6 


I I I . 84 


995 38 


1267.36 


45118.016 


5 9665 


3-2897 


35-7 


112. 15 


1000.98 


1274.49 


45499 293 


5 9749 


3.2927 


35.8 


112.47 


1006.60 


1281.64 


45882.712 


5 9833 


3 . 2958 


35 9 


112.78 


1012.23 


1288.81 


46268.279 


5 9916 


3 2989 


36.0 


113 10 


1017.88 


I 296 . 00 


46656 . 000 


6.0000 


3 3019 


36.1 


"3 41 


1023.54 


1303 21 


47045 881 


6.0083 


3 3050 


36.2 


"3-73 


1029. 22 


1310.44 


47437.928 


6.0166 


3 3080 


36.3 


114.04 


1034 91 


1317.69 


47832.147 


6.0249 


33"! 


36.4 


"4-35 


1040.62 


1324.96 


48228.544 


6.0332 


3.3141 



550 



HEATING AND VENTILATING. 



TABLE W,— Continued, 



n 


nw 


A 


M> 


n> 


V^ 


^ 


Diam. 


Circumf. 


Area. 


Square. 


Cube. 


• Sq. Root. 


Cub. Rt. 


36. 5 


114.67 


1046.35 


1332.25 


48627.125 


6.0415 


3 3171 


36.6 


114.98 


1052.09 


1339 56 


49027.896 


6.0497 


3.3202 


36.7 


"5 30 


1057.84 


1346.89 


49430.863 


6.0580 


3 3^52 


36.8 


115-61 


1063.62 


1354 24 


49836.032 


6.0663 


3 3262 


36 9 


115.92 


1069.41 


1361.61 


50243.409 


6.0745 


3 3292 


370 


116.24 


1075.21 


1369.00 


50653.000 


6.0827 


3-3322 


37.1 


"6.55 


1081.03 


1376.41 


51064. 81 I 


6.0909 


3-3J52 


37.2 


116.87 


1086.87 


1383 . 84 


51478.848 


6.0991 


3 3382 


37 3 


117. 18 


1092.72 


1391 • 29 


51895. 117 


6.1073 


3 3412 


37 4 


117.50 


1098.58 


1398.76 


52313.624 


6-II55 


3-3442 


37.5 


117. 81 


1104.47 


1406.25 


52734 375 


6.1237 


3 3472 


37 6 


118. 12 


1110.36 


1413-76 


53157.376 


6.1318 


3 3501 


37 7 


118.44 


1116.28 


1421 . 29 


53582.633 


6.1400 


3 3531 


37-8 


118.75 


1122.21 


1428.84 


54010.152 


6.1481 


3 3561 


37.9 


119.07 


1128.15 


1436.41 


54439-939 


6.1563 


3-3590 


38 


119.38 


1134.li 


1444 00 


54872.000 


6.1644 


3 3620 


38- 1 


119.69 


I 140 . 09 


145I-61 


55306.341 


6.172^ 


3 3649 


38.2 


120.01 


1146.08 


1459 24 


55742.968 


6.1806 


3 3679 


38.3 


120.32 


1152.09 


1466.89 


56181.887 


6.1887 


3.3708 


38.4 


120.64 


1158.12 


1474.56 


56623 . 104 


6.1967 


3-3737 


38.5 


120.95 


1164.16 


1482.25 


57066.625 


6 . 2048 


3-3767 


38.6 


121.27 


1170.21 


1489.96 


57512.456 


6.2129 


3 3796 


38.7 


121.58 


1176.28 


1497 69 


57960.603 


6.2209 


3.3825 


38.8 


121.89 


1182.37 


1505 44 


58411.072 


6.2289 


3 3854 


38.9 


122.21 


1188.47 


1513-21 


58863.869 


6.2370 


3-3883 


39 


122.52 


"94 59 


1521.00 


59319.000 


6.2450 


3 3912 


39.1 


122.84 


1200.72 


1528.81 


59776.471 


6.2530 


3 3941 


39 2 


123.15 


1206.87 


1536.64 


60236.288 


6.2610 


3 3970 


39 3 


123.46 


1213.04 


1544 49 


60698.457 


6.2689 


3-3999 


39-4 


123.78 


1219.22 


1552.36 


61162.984 


6.2769 


3.4028 


39-5 


124.09 


1225.42 


1560.25 


61629.875 


6 . 2849 


3 4056 


39-^ 


124.41 


1231.63 


1568.16 


62099.136 


6.2928 


3 4085 


39.7 


124.72 


1237-86 


1576.09 


62570.773 


6.3008 


3 4"4 


39-8 


125.04 


1244. 10 


1584.04 


63044-792 


6.3087 


3-4142 


39 9 


125.35 


1250.36 


159201 


63521.199 


6.31